Scanning antenna, scanning antenna drive method, and liquid crystal device

ABSTRACT

A scanning antenna includes a transmission and/or reception region including a plurality of antenna units and a non-transmission and/or reception region located in a region other than the transmission and/or reception region. The scanning antenna includes a TFT substrate, a slot substrate, and a liquid crystal layer provided between the TFT substrate and the slot substrate. The scanning antenna includes: at least one monitoring capacitance section formed in the non-transmission and/or reception region, the section including a liquid crystal layer and a monitoring capacitance, which includes a first measurement electrode and a second measurement electrode opposing each other with the liquid crystal layer interposed therebetween; and a voltage monitor connectable to the first measurement electrode of the monitoring capacitance.

TECHNICAL FIELD

The disclosure relates to a scanning antenna, a scanning antenna driving method, and a liquid crystal device, and more particularly relates to a scanning antenna and a driving method thereof in which an antenna unit (also referred to as an “element antenna”) has a liquid crystal capacitance (also referred to as a “liquid crystal array antenna”).

BACKGROUND ART

Antennas for mobile communication and satellite broadcasting require functions that can change the beam direction (referred to as “beam scanning” or “beam steering”). As an example of an antenna (hereinafter referred to as a “scanning antenna”) having such functionality, phased array antennas equipped with antenna units are known. However, existing phased array antennas are expensive, which is an obstacle for popularization as a consumer product. In particular, as the number of antenna units increases, the cost rises considerably.

Therefore, scanning antennas that utilize the high dielectric anisotropy (birefringence) of liquid crystal materials (including nematic liquid crystals and polymer dispersed liquid crystals) have been proposed (PTL 1 to PTL 5 and NPL 1). Since the dielectric constant of liquid crystal materials has frequency dispersion, in the present specification, the dielectric constant in the microwave frequency band (also referred to as the “dielectric constant for microwaves”) is particularly denoted as “dielectric constant M(ε_(M))”.

PTL 3 and NPL 1 describe how an inexpensive scanning antenna can be obtained by using liquid crystal display (hereinafter referred to as “LCD”) device technology.

CITATION LIST Patent Literature

-   PTL 1: JP 2007-116573 A -   PTL 2: JP 2007-295044 A -   PTL 3: JP 2009-538565 A -   PTL 4: JP 2013-539949 A -   PTL 5: WO 2015/126550

Non Patent Literature

-   NPL 1: R. A. Stevenson et al., “Rethinking Wireless Communications:     Advanced Antenna Design using LCD Technology”, SID 2015 DIGEST, pp.     827-830. -   NPL 2: M. ANDO et al., “A Radial Line Slot Antenna for 12 GHz     Satellite TV Reception”, IEEE Transactions of Antennas and     Propagation, Vol. AP-33, No. 12, pp. 1347-1353 (1985).

SUMMARY Technical Problem

As described above, although the idea of realizing an inexpensive scanning antenna by applying LCD technology is known, there are no documents that specifically describe the structure, the manufacturing method, and the driving method of scanning antennas using LCD technology.

Accordingly, an object of the disclosure is to provide a scanning antenna which can be mass-produced by utilizing existing manufacturing techniques of LCDs and a manufacturing method thereof.

Solution to Problem

A scanning antenna according to an embodiment of the disclosure includes a transmission and/or reception region including a plurality of antenna units and a non-transmission and/or reception region located in a region other than the transmission and/or reception region. The scanning antenna includes: a TFT substrate including a first dielectric substrate, a plurality of TFTs supported by the first dielectric substrate, a plurality of gate bus lines, a plurality of source bus lines, and a plurality of patch electrodes; a slot substrate including: a second dielectric substrate, and a slot electrode formed on a first main surface of the second dielectric substrate; a liquid crystal layer provided between the TFT substrate and the slot substrate; and a reflective conductive plate disposed opposing a second main surface of the second dielectric substrate opposite to the first main surface with a dielectric layer interposed between the reflective conductive plate and the second dielectric substrate. The slot electrode includes: a plurality of slots disposed corresponding to the plurality of patch electrodes, at least one monitoring capacitance section formed in the non-transmission and/or reception region and including the liquid crystal layer and a monitoring capacitance including a first measurement electrode and a second measurement electrode opposing each other with the liquid crystal layer interposed between the first measurement electrode and the second measurement electrode, and a voltage monitor connectable to the first measurement electrode of the monitoring capacitance.

In an embodiment, the scanning antenna further includes a pulse voltage supply circuit including an amplifier electrically connectable to the first measurement electrode; and a feedback circuit configured to negatively feed back an output of the amplifier via the monitoring capacitance.

In an embodiment, the scanning antenna further includes a monitoring auxiliary capacitance electrically connected to the monitoring capacitance.

In an embodiment, the scanning antenna further includes a circuit configured to receive an output of the voltage monitor and obtain a voltage holding ratio of the monitoring capacitance; and a circuit configured to determine, based on the voltage holding ratio, a gray scale voltage to be supplied to each of the plurality of antenna units.

In an embodiment, the first measurement electrode is formed from a conductive film identical to a conductive film of the plurality of patch electrodes; and the second measurement electrode is formed from a conductive film identical to a conductive film of the slot electrode.

In an embodiment, the scanning antenna further includes a sealing portion formed in the non-transmission and/or reception region and surrounding the liquid crystal layer. The first measurement electrode and the second measurement electrode do not overlap a region of less than 10 mm from the sealing portion when viewed from a normal direction of the first dielectric substrate.

In an embodiment, the scanning antenna further includes a sealing portion formed in the non-transmission and/or reception region and surrounding the liquid crystal layer. The TFT substrate or the slot substrate includes a resin structure between the first measurement electrode or the second measurement electrode and the sealing portion.

In an embodiment, the TFT substrate or the slot substrate includes a plurality of columnar metals around the first measurement electrode or the second measurement electrode in the non-transmission and/or reception region; and the plurality of columnar metals include a columnar metal provided between the first measurement electrode or the second measurement electrode and the transmission and/or reception region.

In an embodiment, the scanning antenna further includes a driving circuit configured to receive an input signal providing a gray scale to be exhibited by the plurality of antenna units and to supply a gray scale voltage to each of the plurality of antenna units. The driving circuit can supply a gray scale voltage, based on an output of the voltage monitor.

A method for driving the scanning antenna according to an embodiment of the disclosure includes obtaining, based on an output of the voltage monitor, a voltage holding ratio of the monitoring capacitance; and determining, based on the voltage holding ratio, a gray scale voltage to be supplied to each of the plurality of antenna units.

A liquid crystal device according to an embodiment of the disclosure includes an active region including a plurality of unit regions; and a non-active region located in a region other than the active region. Each of the plurality of unit regions includes a liquid crystal layer and a pair of electrodes provided with the liquid crystal layer interposed between the pair of electrodes and configured to apply a voltage to the liquid crystal layer, at least one monitoring capacitance section formed in the non-active region including the liquid crystal layer and a monitoring capacitance including a first measurement electrode and a second measurement electrode opposing each other with the liquid crystal layer interposed between the first measurement electrode and the second measurement electrode, and a voltage monitor connectable to the first measurement electrode of the monitoring capacitance.

Advantageous Effects of Disclosure

According to an embodiment of the disclosure, provided is a scanning antenna which can be mass-produced by using the existing manufacturing technology of LCDs, and a manufacturing method and a driving method thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating a portion of a scanning antenna 1000 according to a first embodiment.

FIG. 2A and FIG. 2B are schematic plan views illustrating a TFT substrate 101 and a slot substrate 201 in the scanning antenna 1000, respectively.

FIG. 3A and FIG. 3B are a cross-sectional view and a plan view schematically illustrating an antenna unit region U of the TFT substrate 101, respectively.

FIG. 4A to FIG. 4C are cross-sectional views schematically illustrating a gate terminal section GT, a source terminal section ST, and a transfer terminal section PT of the TFT substrate 101, respectively.

FIG. 5 is a diagram illustrating an example of a manufacturing process of the TFT substrate 101.

FIG. 6 is a cross-sectional view schematically illustrating an antenna unit region U and a terminal section IT in the slot substrate 201.

FIG. 7 is a schematic cross-sectional view for illustrating a transfer section in the TFT substrate 101 and the slot substrate 201.

FIG. 8A to FIG. 8C are cross-sectional views illustrating the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT, respectively, of a TFT substrate 102 in a second embodiment.

FIG. 9 is a diagram illustrating an example of a manufacturing process of the TFT substrate 102.

FIG. 10A to FIG. 10C are cross-sectional views illustrating the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT, respectively, of a TFT substrate 103 in a third embodiment.

FIG. 11 is a diagram illustrating an example of a manufacturing process of the TFT substrate 103.

FIG. 12 is a schematic cross-sectional view for illustrating a transfer section in the TFT substrate 103 and a slot substrate 203.

FIG. 13A is a schematic plan view of a TFT substrate 104 including a heater resistive film 68, and FIG. 13B is a schematic plan view for illustrating the sizes of slots 57 and patch electrodes 15.

FIG. 14A and FIG. 14B are diagrams illustrating the schematic structure and current distribution of resistance heating structures 80 a and 80 b.

FIG. 15A to FIG. 15C are diagrams illustrating the schematic structure and current distribution of resistance heating structures 80 c to 80 e.

FIG. 16A is a schematic cross-sectional view of a liquid crystal panel 100Pa including a heater resistive film 68, and FIG. 16B is a schematic cross-sectional view of the liquid crystal panel 100Pb including the heater resistive film 68.

FIG. 17 is a diagram illustrating an equivalent circuit of one antenna unit in a scanning antenna according to an embodiment of the disclosure.

FIG. 18A to FIG. 18C, and FIG. 18E to FIG. 18G are diagrams illustrating examples of waveforms of each signal used for driving the scanning antenna according to an embodiment, and FIG. 18D is a diagram illustrating a waveform of a display signal of an LCD panel performing dot inversion driving.

FIG. 19A to FIG. 19E are diagrams illustrating another example of the waveforms of each signal used for driving the scanning antenna according to an embodiment.

FIG. 20A to FIG. 20E are diagrams illustrating yet another example of the waveforms of each signal used for driving the scanning antenna according to an embodiment.

FIG. 21A and FIG. 21B are schematic diagrams for illustrating a relationship between a reduction in the voltage holding ratio of a liquid crystal capacitance and antenna characteristics.

FIG. 22 is a schematic plan view illustrating a scanning antenna 1000A according to an embodiment of the disclosure.

FIG. 23 is a schematic plan view illustrating a non-transmission and/or reception region R2 of the scanning antenna 1000A.

FIG. 24A and FIG. 24B are schematic cross-sectional views illustrating the non-transmission and/or reception region R2 of the scanning antenna 1000 along the lines A-A′ and B-B′ in FIG. 23, respectively.

FIG. 25A to FIG. 25C are schematic plan views illustrating regions corresponding to the non-transmission and/or reception region R2 of the scanning antenna 1000A illustrated in FIG. 23, where FIG. 25A is a diagram illustrating a gate metal layer, FIG. 25B is a diagram illustrating a patch metal layer, and FIG. 25C is a diagram illustrating a layer including a slot electrode 55.

FIG. 26A is a circuit diagram illustrating a configuration when a VHR monitor circuit MD supplies a pulse voltage to a VHR monitoring capacitance C_(MV), and FIG. 26B is a circuit diagram illustrating a configuration when the VHR monitor circuit MD monitors a change in the potential of a first measurement electrode ME1 of the VHR monitoring capacitance C_(MV).

FIG. 27 is a block diagram schematically illustrating a driving circuit 90 included in the scanning antenna 1000A.

FIG. 28 is a block diagram schematically illustrating a driving circuit 90 included in a scanning antenna 1000B according to an embodiment of the disclosure.

FIG. 29A is a schematic plan view of the non-transmission and/or reception region R2 of a scanning antenna 1000A1 having a resin structure 75A, and FIG. 29B is a schematic plan view of the non-transmission and/or reception region R2 of a scanning antenna 1000A2 having a resin structure 75B.

FIG. 30 is a schematic plan view of a scanning antenna 1000A3 including a columnar metal 77.

FIG. 31 is a schematic plan view of a scanning antenna 1000A4 including the resin structure 75A and the columnar metal 77.

FIG. 32 is a diagram illustrating the results of Experimental Examples 1 to 3.

FIG. 33A is a schematic diagram illustrating a structure of an existing LCD 900, and FIG. 33B is a schematic cross-sectional view of an LCD panel 900 a.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a scanning antenna and a manufacturing method thereof according to embodiments of the disclosure will be described with reference to the drawings. In the following description, first, the structure and manufacturing method of a known TFT-type LCD (hereinafter referred to as a “TFT-LCD”) will be described. However, the description of matters well-known within the technical field of LCDs may be omitted. For a description of basic TFT-LCD technology, please refer to, for example, Liquid Crystals, Applications and Uses, Vol. 1-3 (Editor: Birenda Bahadur, Publisher: World Scientific Pub. Co., Inc.), or the like. For reference, the entire content of the disclosures of the above documents is incorporated herein.

The structure and operation of a typical transmissive TFT-LCD (hereinafter simply referred to as an “LCD”) 900 will be described with reference to FIG. 33A and FIG. 33B. Here, an LCD 900 with a vertical electric field mode (for example, a TN mode or a vertical alignment mode) in which a voltage is applied in a thickness direction of a liquid crystal layer is provided as an example. The frame frequency (which is typically twice the polarity inversion frequency) of the voltage applied to the liquid crystal capacitance of the LCD is 240 Hz even at quad speed driving, for example, and the dielectric constant c of the liquid crystal layer that serves as the dielectric layer of the liquid crystal capacitance of the LCD is different from the dielectric constant M (ε_(M)) with respect to microwaves (for example, satellite broadcasting, the Ku band (from 12 to 18 GHz), the K band (from 18 to 26 GHz), and the Ka band (from 26 to 40 GHz)).

As is schematically illustrated in FIG. 33A, the transmissive LCD 900 includes a liquid crystal display panel 900 a, a control circuit CNTL, a backlight (not illustrated), and a power source circuit (not illustrated). The liquid crystal display panel 900 a includes a liquid crystal display cell LCC and a driving circuit including a gate driver GD and a source driver SD. The driving circuit may be, for example, mounted on a TFT substrate 910 of the liquid crystal display cell LCC, or all or a part of the driving circuit may be integrated (monolithic integration) with the TFT substrate 910.

FIG. 33B is a schematic cross-sectional view of the liquid crystal display panel (hereinafter referred to as an “LCD panel”) 900 a included in the LCD 900. The LCD panel 900 a includes the TFT substrate 910, a counter substrate 920, and a liquid crystal layer 930 provided therebetween. Both the TFT substrate 910 and the counter substrate 920 include transparent substrates 911 and 921, such as glass substrates. In addition to glass substrates, plastic substrates may also be used as the transparent substrates 911 and 921 in some cases. The plastic substrates are formed of, for example, a transparent resin (for example, polyester) and a glass fiber (for example, nonwoven fabric).

A display region DR of the LCD panel 900 a is configured of pixels P arranged in a matrix. A frame region FR that does not serve as a part of the display is formed around the display region DR. The liquid crystal material is sealed in the display region DR by a sealing portion (not illustrated) formed surrounding the display region DR. The sealing portion is formed by curing a sealing material including, for example, an ultraviolet curable resin and a spacer (for example, resin beads or silica beads), and bonds and secures the TFT substrate 910 and the counter substrate 920 to each other. The spacer in the sealing material controls a gap between the TFT substrate 910 and the counter substrate 920, that is, a thickness of the liquid crystal layer 930, to be constant. To suppress an in-plane variation in the thickness of the liquid crystal layer 930, columnar spacers are formed on light blocking portions (for example, on a wiring line) in the display region DR by using an ultraviolet curable resin. In recent years, as seen in LCD panels for liquid crystal televisions and smart phones, a width of the frame region FR that does not serve as part of the display is very narrow.

In the TFT substrate 910, a TFT 912, a gate bus line (scanning line) GL, a source bus line (display signal line) SL, a pixel electrode 914, an auxiliary capacitance electrode (not illustrated), and a CS bus line (auxiliary capacitance line) (not illustrated) are formed on the transparent substrate 911. The CS bus line is provided parallel to the gate bus line. Alternatively, the gate bus line of the next stage may be used as the CS bus line (CS on-gate structure).

The pixel electrode 914 is covered with an alignment film (for example, a polyimide film) for controlling the alignment of the liquid crystals. The alignment film is provided so as to be in contact with the liquid crystal layer 930. The TFT substrate 910 is often disposed on the backlight side (the side opposite to the viewer).

The counter substrate 920 is often disposed on the observer side of the liquid crystal layer 930. The counter substrate 920 includes a color filter layer (not illustrated), a counter electrode 924, and an alignment film (not illustrated) on the transparent substrate 921. Since the counter electrode 924 is provided in common to a plurality of pixels P constituting the display region DR, it is also referred to as a common electrode. The color filter layer includes a color filter (for example, a red filter, a green filter, and a blue filter) provided for each pixel P, and a black matrix (light shielding layer) for blocking light unnecessary for display. The black matrix is arranged, for example, so as to block light between the pixels P in the display region DR and at the frame region FR.

The pixel electrode 914 of the TFT substrate 910, the counter electrode 924 of the counter substrate 920, and the liquid crystal layer 930 therebetween constitute a liquid crystal capacitance Clc. Individual liquid crystal capacitances correspond to the pixels. To retain the voltage applied to the liquid crystal capacitance Clc (so as to increase what is known as the voltage holding ratio), an auxiliary capacitance CS electrically connected in parallel with the liquid crystal capacitance Clc is formed. The auxiliary capacitance CS is typically composed of an electrode having the same potential as the pixel electrode 914, an inorganic insulating layer (for example, a gate insulating layer (SiO₂ layer)), and an auxiliary capacitance electrode connected to the CS bus line. Typically, the same common voltage as the counter electrode 924 is supplied from the CS bus line.

Factors responsible for lowering the voltage (effective voltage) applied to the liquid crystal capacitance Clc are (1) those based on the CR time constant which is the product of the capacitance value C_(clc) of the liquid crystal capacitance Clc and the resistance value R, and (2) interfacial polarization due to ionic impurities included in the liquid crystal material and/or the orientation polarization of the liquid crystal molecules. Among these, the contribution of the CR time constant of the liquid crystal capacitance Clc is large, and the CR time constant can be increased by providing an auxiliary capacitance CS electrically connected in parallel with the liquid crystal capacitance Clc. Note that the volume resistivity of the liquid crystal layer 930 that serves as the dielectric layer of the liquid crystal capacitance Clc exceeds the order of 10¹²Ω·cm in the case of widely used nematic liquid crystal materials.

A display signal supplied to the pixel electrode 914 is a display signal that is supplied to the source bus line SL connected to the TFT 912 when the TFT 912, selected by a scanning signal supplied from the gate driver GD to the gate bus line GL, is turned on. Accordingly, the TFTs 912 connected to a particular gate bus line GL are simultaneously turned on, and at that time, corresponding display signals are supplied from the source bus lines SL connected to the respective TFTs 912 of the pixels P in that row. By performing this operation sequentially from the first row (for example, the uppermost row of a display surface) to the mth row (for example, the lowermost row of the display surface), one image (frame) is written in the display region DR composed of m rows of pixels and is displayed. Assuming that the pixels P are arranged in a matrix of m rows and n columns, at least n source bus lines SL are provided in total such that at least one source bus line SL corresponds to each pixel column.

Such scanning is referred to as line-sequential scanning, a time between one pixel row being selected and the next pixel row being selected is called a horizontal scan period, (1H), and a time between a particular row being selected and then being selected a second time is called a vertical scanning period, (1V), or a frame. Note that, in general, 1V (or 1 frame) is obtained by adding the blanking period to the period m·H for selecting all m pixel rows.

For example, when an input video signal is an NTSC signal, 1V (=1 frame) of an existing LCD panel is 1/60 of a second (16.7 milliseconds). The NTSC signals are interlaced signals, the frame frequency is 30 Hz, and the field frequency is 60 Hz, but in LCD panels, since it is necessary to supply display signals to all the pixels in each field, they are driven with 1V=( 1/60) second (driven at 60 Hz). Note that, in recent years, to improve the video display characteristics, there are LCD panels driven at double speed drive (120 Hz drive, 1V=( 1/120 second)), and some LCD panels are driven at quad speed (240 Hz drive, 1V=( 1/240 second)) for 3D displays.

When a DC voltage is applied to the crystal layer 930, the effective voltage decreases and the luminance of the pixel P decreases. Since the above-mentioned interface polarization and/or the orientation polarization contribute to the decrease in the effective voltage, it is difficult for the auxiliary capacitance CS to prevent the decrease in the effective voltage completely. For example, when a display signal corresponding to a particular intermediate gray scale is written into every pixel in every frame, the luminance fluctuates for each frame and is observed as flicker. In addition, when a DC voltage is applied to the liquid crystal layer 930 for an extended period of time, electrolysis of the liquid crystal material may occur. Furthermore, impurity ions segregate at one side of the electrode, so that the effective voltage may not be applied to the liquid crystal layer and the liquid crystal molecules may not move. To prevent this, the LCD panel 900 a is subjected to so-called AC driving. Typically, frame-reversal driving is performed in which the polarity of the display signal is inverted every frame (every vertical scanning period). For example, in existing LCD panels, the polarity inversion is performed every 1/60 seconds (a polarity inversion cycle is 30 Hz).

In addition, dot inversion driving, line reversal driving, or the like is performed in order to uniformly distribute the pixels having different polarities of applied voltages even within one frame. This is because it is difficult to completely match the magnitude of the effective voltage applied to the liquid crystal layer between a positive polarity and a negative polarity. For example, in a case where the volume resistivity of the liquid crystal material exceeds the order of 10¹²Ω·cm, flicker is hardly recognizable in a case where dot inversion or line reversal driving is performed every 1/60 seconds.

With respect to the scanning signal and the display signal in the LCD panel 900 a, on the basis of the signals supplied from the control circuit CNTL to the gate driver GD and the source driver SD, the gate driver GD and the source driver SD supply the scanning signal and the display signal to the gate bus line GL and the source bus line SL, respectively. For example, the gate driver GD and the source driver SD are each connected to corresponding terminals provided on the TFT substrate 910. The gate driver GD and the source driver SD may be mounted on the frame region FR of the TFT substrate 910 as a driver IC, for example, or may be monolithically formed in the frame region FR of the TFT substrate 910.

The counter electrode 924 of the counter substrate 920 is electrically connected to a terminal (not illustrated) of the TFT substrate 910 with a conductive portion (not illustrated) known as a transfer therebetween. The transfer is formed, for example, so as to overlap with the sealing portion, or alternatively so as to impart conductivity to a part of the sealing portion. This is done to narrow the frame region FR. A common voltage is directly or indirectly supplied to the counter electrode 924 from the control circuit CNTL. Typically, the common voltage is also supplied to the CS bus line as described above.

Basic Structure of Scanning Antenna

By controlling the voltage applied to each liquid crystal layer of each antenna unit corresponding to the pixels of the LCD panel and changing the effective dielectric constant M (ε_(M)) of the liquid crystal layer for each antenna unit, a scanning antenna equipped with an antenna unit that uses the anisotropy (birefringence index) of a large dielectric constant M (ε_(M)) of a liquid crystal material forms a two-dimensional pattern by antenna units with different electrostatic capacitances (corresponding to displaying an image by an LCD). An electromagnetic wave (for example, a microwave) emitted from an antenna or received by an antenna is given a phase difference depending on the electrostatic capacitance of each antenna unit, and gains a strong directivity in a particular direction depending on the two-dimensional pattern formed by the antenna units having different electrostatic capacitances (beam scanning). For example, an electromagnetic wave emitted from an antenna is obtained by integrating, with consideration for the phase difference provided by each antenna unit, the spherical waves obtained as a result of input electromagnetic waves entering each antenna unit and being scattered by each antenna unit. It can be considered that each antenna unit functions as a “phase shifter”. For a description of the basic structure and operating principles of a scanning antenna that uses a liquid crystal material, refer to PTL 1 to PTL 4 as well as NPL 1 and NPL 2. NPL 2 discloses the basic structure of a scanning antenna in which spiral slots are arranged. For reference, the entire content of the disclosures of PTL 1 to PTL 4 as well as NPL 1 and NPL 2 is incorporated herein.

Note that although the antenna units in the scanning antenna according to the embodiments of the disclosure are similar to the pixels of the LCD panel, the structure of the antenna units is different from the structure of the pixel of the LCD panel, and the arrangement of the plurality of antenna units is also different from the arrangement of the pixels in the LCD panel. A basic structure of the scanning antenna according to the embodiments of the disclosure will be described with reference to FIG. 1, which illustrates a scanning antenna 1000 of a first embodiment to be described in detail later. Although the scanning antenna 1000 is a radial in-line slot antenna in which slots are concentrically arranged, the scanning antennas according to the embodiments of the disclosure are not limited to this. For example, the arrangement of the slots may be any of the various known arrangements. In particular, with respect to the slot and/or antenna unit arrangements, the entire disclosure of PTL 5 is incorporated herein by reference.

FIG. 1 is a cross-sectional view schematically illustrating a portion of the scanning antenna 1000 of the present embodiment, and schematically illustrates a part of the cross-section along the radial direction from a power feed pin 72 (see FIG. 2B) provided near the center of the concentrically arranged slots.

The scanning antenna 1000 includes a TFT substrate 101, a slot substrate 201, a liquid crystal layer LC provided therebetween, and a reflective conductive plate 65 opposing the slot substrate 201 with an air layer 54 interposed between the slot substrate 201 and the reflective conductive plate 65. The scanning antenna 1000 transmits and receives microwaves from a side closer to the TFT substrate 101.

The TFT substrate 101 includes a dielectric substrate 1 such as a glass substrate, a plurality of patch electrodes 15 and a plurality of TFTs 10 formed on the dielectric substrate 1. Each patch electrode 15 is connected to a corresponding TFT 10. Each TFT 10 is connected to a gate bus line and a source bus line.

The slot substrate 201 includes a dielectric substrate 51 such as a glass substrate and a slot electrode 55 formed on a side of the dielectric substrate 51 closer to the liquid crystal layer LC. The slot electrode 55 includes a plurality of slots 57.

The reflective conductive plate 65 is disposed opposing the slot substrate 201 with the air layer 54 interposed between the reflective conductive plate 65 and the slot substrate 201. In place of the air layer 54, a layer formed of a dielectric (for example, a fluorine resin such as PTFE) having a small dielectric constant M for microwaves can be used. The slot electrode 55, the reflective conductive plate 65, and the dielectric substrate 51 and the air layer 54 therebetween function as a waveguide 301.

The patch electrode 15, the portion of the slot electrode 55 including the slot 57, and the liquid crystal layer LC therebetween constitute an antenna unit U. In each antenna unit U, one patch electrode 15 is opposed to a portion of the slot electrode 55 including one slot 57 with a liquid crystal layer LC interposed therebetween, thereby constituting the liquid crystal capacitance. The structure in which the patch electrode 15 and the slot electrode 55 oppose each other with the liquid crystal layer LC interposed therebetween is similar to the structure illustrated in FIG. 33A and FIG. 33B in which the pixel electrode 914 and the counter electrode 924 of the LCD panel 900 a oppose each other with the liquid crystal layer 930 interposed therebetween. That is, the antenna unit U of the scanning antenna 1000 and the pixel P of the LCD panel 900 a have a similar configuration. In addition, the antenna unit has a configuration similar to that of the pixel P in the LCD panel 900 a in that the antenna unit has an auxiliary capacitance electrically connected in parallel with the liquid crystal capacitance (see FIG. 13A and FIG. 17). However, the scanning antenna 1000 has many differences from the LCD panel 900 a.

First, the performance required for the dielectric substrates 1 and 51 of the scanning antenna 1000 is different from the performance required for the substrate of the LCD panel.

Generally, transparent substrates that are transparent to visible light are used for LCD panels. For example, glass substrates or plastic substrates are used. In reflective LCD panels, since the substrate on the back side does not need transparency, a semiconductor substrate may be used in some cases. In contrast to this, it is preferable for the dielectric substrates 1 and 51 used for the antennas to have small dielectric losses with respect to microwaves (where the dielectric tangent with respect to microwaves is denoted as tan δ_(M)). The tan δ_(M) of the dielectric substrates 1 and 51 is preferably approximately less than or equal to 0.03, and more preferably less than or equal to 0.01. Specifically, a glass substrate or a plastic substrate can be used. Glass substrates are superior to plastic substrates with respect to dimensional stability and heat resistance, and are suitable for forming circuit elements such as TFTs, a wiring line, and electrodes using LCD technology. For example, in a case where the materials forming the waveguide are air and glass, as the dielectric loss of glass is greater, from the viewpoint that thinner glass can reduce the waveguide loss, it is preferable for the thickness to be less than or equal to 400 μm, and more preferably less than or equal to 300 μm. There is no particular lower limit, provided that the glass can be handled such that it does not break in the manufacturing process.

The conductive material used for the electrode is also different. In many cases, an ITO film is used as a transparent conductive film for pixel electrodes and counter electrodes of LCD panels. However, ITO has a large tan SM with respect to microwaves, and as such cannot be used as the conductive layer in an antenna. The slot electrode 55 functions as a wall for the waveguide 301 together with the reflective conductive plate 65. Accordingly, to suppress the transmission of microwaves in the wall of the waveguide 301, it is preferable that the thickness of the wall of the waveguide 301, that is, the thickness of the metal layer (Cu layer or Al layer) be large. It is known that in a case where the thickness of the metal layer is three times the skin depth, electromagnetic waves are attenuated to 1/20 (−26 dB), and in a case where the thickness is five times the skin depth, electromagnetic waves are attenuated to about 1/150 (−43 dB). Accordingly, in a case where the thickness of the metal layer is five times the skin depth, the transmittance of electromagnetic waves can be reduced to 1%. For example, for a microwave of 10 GHz, in a case where a Cu layer having a thickness of greater than or equal to 3.3 μm and an Al layer having a thickness of greater than or equal to 4.0 μm are used, microwaves can be reduced to 1/150. In addition, for a microwave of 30 GHz, in a case where a Cu layer having a thickness of greater than or equal to 1.9 μm and an Al layer having a thickness of greater than or equal to 2.3 μm are used, microwaves can be reduced to 1/150. In this way, the slot electrode 55 is preferably formed of a relatively thick Cu layer or Au layer. There is no particular upper limit for the thickness of the Cu layer or the Al layer, and the thicknesses can be set appropriately in consideration of the time and cost of film formation. The usage of a Cu layer provides the advantage of being thinner than the case of using an Al layer. Relatively thick Cu layers or Al layers can be formed not only by the thin film deposition method used in LCD manufacturing processes, but also by other methods such as bonding Cu foil or Al foil to the substrate. The thickness of the metal layer, for example, ranges from 2 μm to 30 μm. When the thin film deposition methods are used, the thickness of the metal layer is preferably less than or equal to 5 μm. Note that aluminum plates, copper plates, or the like having a thickness of several mm can be used as the reflective conductive plate 65, for example.

Since the patch electrode 15 does not configure the waveguide 301 like the slot electrode 55, a Cu layer or an Al layer having a smaller thickness than that of the slot electrode 55 can be used. However, to avoid losses caused by heat when the oscillation of free electrons near the slot 57 of the slot electrode 55 induces the oscillation of the free electrons in the patch electrode 15, it is preferable that the resistance be low. From the viewpoint of mass production, it is preferable to use an Al layer rather than a Cu layer, and the thickness of the Al layer is preferably greater than or equal to 0.3 μm and less than or equal to 2 μm, for example.

In addition, an arrangement pitch of the antenna units U is considerably different from that of a pixel pitch. For example, considering an antenna for microwaves of 12 GHz (Ku band), the wavelength λ is 25 mm, for example. Then, as described in PTL 4, since the pitch of the antenna unit U is less than or equal to λ/4 and/or less than or equal to λ/5, the arrangement pitch becomes less than or equal to 6.25 mm and/or less than or equal to 5 mm. This is ten times greater than the pixel pitch of the LCD panel. Accordingly, the length and width of the antenna unit U are also roughly ten times greater than the pixel length and width of the LCD panel.

Of course, the arrangement of the antenna units U may be different from the arrangement of the pixels in the LCD panel. Herein, although an example is illustrated in which the antenna units U are arranged in concentric circles (for example, refer to JP 2002-217640 A), the present disclosure is not limited thereto, and the antenna units may be arranged in a spiral shape as described in NPL 2, for example. Furthermore, the antenna units may be arranged in a matrix as described in PTL 4.

The properties required for the liquid crystal material of the liquid crystal layer LC of the scanning antenna 1000 are different from the properties required for the liquid crystal material of the LCD panel. In the LCD panel, a change in a refractive index of the liquid crystal layer of the pixels allows a phase difference to be provided to the polarized visible light (wavelength of from 380 nm to 830 nm) such that the polarization state is changed (for example, the change in the refractive index allows the polarization axis direction of linearly polarized light to be rotated or the degree of circular polarization of circularly polarized light to be changed), whereby display is performed. In contrast, in the scanning antenna 1000 according to the embodiment, the phase of the microwave excited (re-radiated) from each patch electrode is changed by changing the electrostatic capacitance value of the liquid crystal capacitance of the antenna unit U. Accordingly, the liquid crystal layer preferably has a large anisotropy (Δε_(M)) of the dielectric constant M (ε_(M)) with respect to microwaves, and tan δ_(M) is preferably small. For example, the Δε_(M) of greater than or equal to 4 and tan δ_(M) of less than or equal to 0.02 (values of 19 GHz in both cases) described in SID 2015 DIGEST pp. 824-826 written by M. Witteck et al, can be suitably used. In addition, it is possible to use a liquid crystal material having a Δε_(M) of greater than or equal to 0.4 and a tan δ_(M) of less than or equal to 0.04 as described in POLYMERS 55 vol. August issue pp. 599-602 (2006), written by Kuki.

In general, the dielectric constant of a liquid crystal material has frequency dispersion, but the dielectric anisotropy Δε_(M) for microwaves has a positive correlation with the refractive index anisotropy Δn with respect to visible light. Accordingly, it can be said that a material having a large refractive index anisotropy Δn with respect to visible light is preferable as a liquid crystal material for an antenna unit for microwaves. The refractive index anisotropy Δn of the liquid crystal material for LCDs is evaluated by the refractive index anisotropy for light having a wavelength of 550 nm. Here again, when a Δn (birefringence index) is used as an index for light having a wavelength of 550 nm, a nematic liquid crystal having a Δn of greater than or equal to 0.3, preferably greater than or equal to 0.4, can be used for an antenna unit for microwaves. Δn has no particular upper limit. However, since liquid crystal materials having a large Δn tend to have a strong polarity, there is a possibility that reliability may decrease. From the viewpoint of reliability, Δn is preferably less than or equal to 0.4. The thickness of the liquid crystal layer is, for example, from 1 μm to 500 μm.

Hereinafter, the structure and manufacturing method of the scanning antenna according to the embodiments of the disclosure will be described in more detail.

First Embodiment

First, a description is given with reference to FIG. 1 and FIGS. 2A and 2B. FIG. 1 is a schematic partial cross-sectional view of the scanning antenna 1000 near the center thereof as described above, and FIG. 2A and FIG. 2B are schematic plan views illustrating the TFT substrate 101 and the slot substrate 201 in the scanning antenna 1000, respectively.

The scanning antenna 1000 includes a plurality of antenna units U arranged two-dimensionally. In the scanning antenna 1000 exemplified here, the plurality of antenna units are arranged concentrically. In the following description, the region of the TFT substrate 101 and the region of the slot substrate 201 corresponding to the antenna units U will be referred to as “antenna unit region”, and be denoted with the same reference numeral U as the antenna units. In addition, as illustrated in FIG. 2A and FIG. 2B, in the TFT substrate 101 and the slot substrate 201, a region defined by the plurality of two-dimensionally arranged antenna unit regions is referred to as “transmission and/or reception region R1”, and a region other than the transmission and/or reception region R1 is called a “non-transmission and/or reception region R2”. A terminal section, a driving circuit, and the like are provided in the non-transmission and/or reception region R2.

FIG. 2A is a schematic plan view illustrating the TFT substrate 101 in the scanning antenna 1000.

In the illustrated example, the transmission and/or reception region R1 has a donut-shape when viewed from a normal direction of the TFT substrate 101. The non-transmission and/or reception region R2 includes a first non-transmission and/or reception region R2 a located at the center of the transmission and/or reception region R1 and a second non-transmission and/or reception region R2 b located at the periphery of the transmission and/or reception region R1. An outer diameter of the transmission and/or reception region R1, for example, is from 200 mm to 1500 mm, and is configured according to a data traffic volume or the like.

A plurality of gate bus lines GL and a plurality of source bus lines SL supported by the dielectric substrate 1 are provided in the transmission and/or reception region R1 of the TFT substrate 101, and the antenna unit regions U are defined by these wiring lines. The antenna unit regions U are, for example, arranged concentrically in the transmission and/or reception region R1. Each of the antenna unit regions U includes a TFT and a patch electrode electrically connected to the TFT. The source electrode of the TFT is electrically connected to the source bus line SL, and the gate electrode is electrically connected to the gate bus line GL. In addition, the drain electrode is electrically connected to the patch electrode.

In the non-transmission and/or reception region R2 (R2 a, R2 b), a seal region Rs is disposed surrounding the transmission and/or reception region R1. A sealing material (not illustrated) is applied to the seal region Rs. The sealing material bonds the TFT substrate 101 and the slot substrate 201 to each other, and also encloses liquid crystals between these substrates 101, 201.

A gate terminal section GT, the gate driver GD, a source terminal section ST, and the source driver SD are provided outside the sealing region Rs in the non-transmission and/or reception region R2. Each of the gate bus lines GL is connected to the gate driver GD with the gate terminal section GT therebetween. Each of the source bus lines SL is connected to the source driver SD with the source terminal section ST therebetween. Note that, in this example, although the source driver SD and the gate driver GD are formed on the dielectric substrate 1, one or both of these drivers may be provided on another dielectric substrate.

Also, a plurality of transfer terminal sections PT are provided in the non-transmission and/or reception region R2. The transfer terminal section PT is electrically connected to the slot electrode 55 (FIG. 2B) of the slot substrate 201. In the present specification, the connection section between the transfer terminal section PT and the slot electrode 55 is referred to as a “transfer section”. As illustrated in drawings, the transfer terminal section PT (transfer section) may be disposed in the seal region Rs. In this case, a resin containing conductive particles may be used as the sealing material. In this way, liquid crystals are sealed between the TFT substrate 101 and the slot substrate 201, and an electrical connection can be secured between the transfer terminal section PT and the slot electrode 55 of the slot substrate 201. In this example, although a transfer terminal section PT is disposed in both the first non-transmission and/or reception region R2 a and the second non-transmission and/or reception region R2 b, the transfer terminal section PT may be disposed in only one of them.

Note that the transfer terminal section PT (transfer section) does not need to be disposed in the seal region Rs. For example, the transfer terminal section PT may be disposed outside the seal region Rs in the non-transmission and/or reception region R2.

FIG. 2B is a schematic plan view illustrating the slot substrate 201 in the scanning antenna 1000, and illustrates the surface of the slot substrate 201 closer to the liquid crystal layer LC.

In the slot substrate 201, the slot electrode 55 is formed on the dielectric substrate 51 extending across the transmission and/or reception region R1 and the non-transmission and/or reception region R2.

In the transmission and/or reception region R1 of the slot substrate 201, the plurality of slots 57 are formed in the slot electrode 55. The slots 57 are formed corresponding to the antenna unit region U on the TFT substrate 101. For the plurality of slots 57 in the illustrated example, a pair of slots 57 extending in directions substantially orthogonal to each other are concentrically disposed so that a radial inline slot antenna is configured. Since the scanning antenna 1000 includes slots that are substantially orthogonal to each other, the scanning antenna 1000 can transmit and receive circularly polarized waves.

A plurality of terminal sections IT of the slot electrode 55 are provided in the non-transmission and/or reception region R2. The terminal section IT is electrically connected to the transfer terminal section PT (FIG. 2A) of the TFT substrate 101. In this example, the terminal section IT is disposed within the seal region Rs. and is electrically connected to a corresponding transfer terminal section PT by a sealing material containing conductive particles.

In addition, the power feed pin 72 is disposed on a rear surface side of the slot substrate 201 in the first non-transmission and/or reception region R2 a. The power feed pin 72 allows microwaves to be inserted into the waveguide 301 constituted by the slot electrode 55, the reflective conductive plate 65, and the dielectric substrate 51. The power feed pin 72 is connected to a power feed device 70. Power feeding is performed from the center of the concentric circle in which the slots 57 are arranged. The power feed method may be either a direct coupling power feed method or an electromagnetic coupling method, and a known power feed structure can be utilized.

In FIG. 2A and FIG. 2B, an example is illustrated in which the seal region Rs is provided so as to surround a relatively narrow region including the transmission and/or reception region R1, but the arrangement of the seal region Rs is not limited to this. In particular, the seal region Rs provided outside the transmission and/or reception region R1 may be provided nearby the side of the dielectric substrate 1 and/or the dielectric substrate 51, for example, so as to maintain a certain distance or more from the transmission and/or reception region R1. Of course, the terminal section and the driving circuit, for example, that are provided in the non-transmission and/or reception region R2 may be formed outside the seal region Rs (that is, the side where the liquid crystal layer is not present). By forming the seal region Rs at a position separated from the transmission and/or reception region R1 by a certain distance or more, it is possible to prevent the antenna characteristics from deteriorating due to the influence of impurities (in particular, ionic impurities) contained in the sealing material (in particular, a curable resin).

In the following, each component of the scanning antenna 1000 will be described in detail with reference to drawings.

Structure of TFT Substrate 101

Antenna Unit Region U

FIG. 3A and FIG. 3B are a cross-sectional view and a plane view schematically illustrating the antenna unit region U of the TFT substrate 101, respectively.

Each of the antenna unit regions U includes a dielectric substrate (not illustrated), a TFT 10 supported by the dielectric substrate, a first insulating layer 11 covering the TFT 10, a patch electrode 15 formed on the first insulating layer 11 and electrically connected to the TFT 10, and a second insulating layer 17 covering the patch electrode 15. The TFT 10 is disposed, for example, at or near an intersection of the gate bus line GL and the source bus line SL.

The TFT 10 include a gate electrode 3, an island-shaped semiconductor layer 5, a gate insulating layer 4 disposed between the gate electrode 3 and the semiconductor layer 5, a source electrode 7S, and a drain electrode 7D. The structure of the TFT 10 is not particularly limited to a specific structure. In this example, the TFT 10 is a channel etch-type TFT having a bottom gate structure.

The gate electrode 3 is electrically connected to the gate bus line GL, and a scanning signal is supplied via the gate bus line GL. The source electrode 7S is electrically connected to the source bus line SL, and a data signal is supplied via the source bus line SL. The gate electrode 3 and the gate bus line GL may be formed of the same conductive film (gate conductive film). The source electrode 7S, the drain electrode 7D, and the source bus line SL may be formed from the same conductive film (source conductive film). The gate conductive film and the source conductive film are, for example, metal films. In the present specification, layers formed using a gate conductive film may be referred to as “gate metal layers”, and layers formed using a source conductive film may be referred to as “source metal layers”.

The semiconductor layer 5 is disposed overlapping with the gate electrode 3 with the gate insulating layer 4 interposed therebetween. In the illustrated example, a source contact layer 6S and a drain contact layer 6D are formed on the semiconductor layer 5. The source contact layer 6S and the drain contact layer 6D are disposed on both sides of a region where a channel is formed in the semiconductor layer 5 (channel region). The semiconductor layer 5 may be an intrinsic amorphous silicon (i-a-Si) layer, and the source contact layer 6S and the drain contact layer 6D may be n⁺ type amorphous silicon (n⁺-a-Si) layers.

The source electrode 7S is provided in contact with the source contact layer 6S and is connected to the semiconductor layer 5 with the source contact layer 6S interposed therebetween. The drain electrode 7D is provided in contact with the drain contact layer 6D and is connected to the semiconductor layer 5 with the drain contact layer 6D interposed therebetween.

The first insulating layer 11 includes a contact hole CH1 that at least reaches the drain electrode 7D of the TFT 10.

The patch electrode 15 is provided on the first insulating layer 11 and within the contact hole CH1, and is in contact with the drain electrode 7D in the contact hole CH1. The patch electrode 15 includes a metal layer. The patch electrode 15 may be a metal electrode formed only from a metal layer. The material of the patch electrode 15 may be the same as those of the source electrode 7S and the drain electrode 7D. However, a thickness of the metal layer in the patch electrode 15 (a thickness of the patch electrode 15 when the patch electrode 15 is a metal electrode) is set to be greater than thicknesses of the source electrode 7S and the drain electrode 7D. The thickness of the metal layer in the patch electrode 15 is set to, for example, greater than or equal to 0.3 μm when it is formed of an Al layer.

A CS bus line CL may be provided using the same conductive film as that of the gate bus line GL. The CS bus line CL may be disposed overlapping with the drain electrode (or extended portion of the drain electrode) 7D with the gate insulating layer 4 interposed therebetween, and may constitute the auxiliary capacitance CS having the gate insulating layer 4 as a dielectric layer.

An alignment mark (for example, a metal layer) 21 and a base insulating film 2 covering the alignment mark 21 may be formed at a position closer to the dielectric substrate than a position of the gate bus line GL. The alignment mark 21 is used as follows. When manufacturing m TFT substrates from one glass substrate, in a case where the number of photomasks is n (where n<m), for example, it is necessary to perform each exposure process multiple times. In this way, when the number (n) of photomasks is less than the number (m) of TFT substrates 101 manufactured from one glass substrate 1, the alignment mark 21 can be used for alignment of the photomasks. The alignment marks 21 may be omitted.

In the present embodiment, the patch electrode 15 is formed in a layer different from the source metal layer. This provides the advantages described below.

Since the source metal layer is typically formed using a metal film, it is conceivable to form a patch electrode in the source metal layer. However, it is preferable that the patch electrode have a low resistance to the extent that the vibration of electrons is not hindered. The patch electrode is formed of a comparatively thick Al layer having a thickness of greater than or equal to 0.3 μm, for example. From the viewpoint of antenna performance, it is preferable that the patch electrode be thick. Depending on the configuration of the TFT, however, when a patch electrode having a thickness exceeding 1 μm is formed in the source metal layer, a problem arises in that the desired patterning accuracy cannot be obtained. For example, there may be a problem that the gap between the source electrode and the drain electrode (corresponding to the channel length of the TFT) cannot be controlled with high accuracy. In contrast, in the present embodiment, since the patch electrode 15 is formed separately from the source metal layer, the thickness of the source metal layer and the thickness of the patch electrode 15 can be controlled independently. This allows the controllability for forming the source metal layer to be secured and a patch electrode 15 having a desired thickness to be formed.

In the present embodiment, the thickness of the patch electrode 15 can be set with a high degree of freedom separately from the thickness of the source metal layer. Note that since the size of the patch electrode 15 does not need to be controlled as strictly as the source bus line SL or the like, it is acceptable for a shift in the line width (deviation from the design value) to be increased by thickening the patch electrode 15. Note that a case where the thickness of the patch electrode 15 is equal to the thickness of the source metal layer is not excluded.

The patch electrode 15 may include a Cu layer or an Al layer as a main layer. A performance of the scanning antenna correlates with an electric resistance of the patch electrode 15, and a thickness of the main layer is set so as to obtain a desired resistance. In terms of the electric resistance, there is a possibility that the thickness of the patch electrode 15 can be made thinner in the Cu layer than in the Al layer.

Gate Terminal Section GT, Source Terminal Section ST, and Transfer Terminal Section PT

FIG. 4A to FIG. 4C are cross-sectional views schematically illustrating the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT, respectively.

The gate terminal section GT includes a gate bus line GL formed on the dielectric substrate, an insulating layer covering the gate bus line GL, and a gate terminal upper connection section 19 g. The gate terminal upper connection section 19 g is in contact with the gate bus line GL within the contact hole CH2 formed in the insulating layer. In this example, the insulating layer covering the gate bus line GL includes the gate insulating layer 4, the first insulating layer 11 and the second insulating layer 17 in that order from the dielectric substrate. The gate terminal upper connection section 19 g is, for example, a transparent electrode formed of a transparent conductive film provided on the second insulating layer 17.

The source terminal section ST includes the source bus line SL formed on the dielectric substrate (here, on the gate insulating layer 4), the insulating layer covering the source bus line SL, and the source terminal upper connection section 19 s. The source terminal upper connection section 19 s is in contact with the source bus line SL within the contact hole CH3 formed in the insulating layer. In this example, the insulating layer covering the source bus line SL includes the first insulating layer 11 and the second insulating layer 17. The source terminal upper connection section 19 s is, for example, a transparent electrode formed of a transparent conductive film provided on the second insulating layer 17.

The transfer terminal section PT include a patch connection section 15 p formed on the first insulating layer 11, the second insulating layer 17 covering the patch connection section 15 p, and a transfer terminal upper connection section 19 p. The transfer terminal upper connection section 19 p is in contact with the patch connection section 15 p within a contact hole CH4 formed in the second insulating layer 17. The patch connection section 15 p is formed of the same conductive film as that of the patch electrode 15. The transfer terminal upper connection section (also referred to as an upper transparent electrode) 19 p is, for example, a transparent electrode formed of a transparent conductive film provided on the second insulating layer 17. In the present embodiment, the upper connection sections 19 g, 19 s, and 19 p for the respective terminal sections are formed of the same transparent conductive film.

In the present embodiment, it is advantageous that the contact holes CH2, CH3, and CH4 of the respective terminal sections can be simultaneously formed by the etching process after the formation of the second insulating layer 17. The detailed manufacturing process thereof will be described later.

Manufacturing Method of TFT Substrate 101

As an example, the TFT substrate 101 can be manufactured by the following method. FIG. 5 is a diagram exemplifying the manufacturing process of the TFT substrate 101.

First, a metal film (for example, a Ti film) is formed on a dielectric substrate and patterned to form an alignment mark 21. For example, a glass substrate, a plastic substrate (resin substrate) having heat resistance, or the like can be used as the dielectric substrate. Next, the base insulating film 2 is formed so as to cover the alignment mark 21. An SiO₂ film is used as the base insulating film 2.

Subsequently, a gate metal layer including the gate electrode 3 and the gate bus line GL is formed on the base insulating film 2.

The gate electrode 3 can be formed integrally with the gate bus line GL. Here, a not-illustrated gate conductive film (with a thickness of greater than or equal to 50 nm and less than or equal to 500 nm) is formed on the dielectric substrate by a sputtering method or the like. Next, the gate conductive film is patterned to obtain the gate electrode 3 and the gate bus line GL. The material of the gate conductive film is not particularly limited to a specific material. A film containing a metal such as aluminum (Al), tungsten (W), molybdenum (Mo), tantalum (Ta), chromium (Cr), titanium (Ti), or copper (Cu), an alloy thereof, or alternatively a metal nitride thereof can be appropriately used. Here, as a gate conductive film, a layered film is formed by layering MoN (having a thickness of 50 nm, for example), Al (having a thickness of 200 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order.

Next, the gate insulating layer 4 is formed so as to cover the gate metal layer. The gate insulating layer 4 can be formed by a CVD method or the like. As the gate insulating layer 4, a silicon oxide (SiO₂) layer, a silicon nitride (SiNx) layer, a silicon oxynitride (SiOxNy; x>y) layer, a silicon nitride oxide (SiNxOy; x>y) layer, or the like may be used as appropriate. The gate insulating layer 4 may have a layered structure. Here, a SiNx layer (having a thickness of 410 nm, for example) is formed as the gate insulating layer 4.

Next, the semiconductor layer 5 and a contact layer are formed on the gate insulating layer 4. Here, an intrinsic amorphous silicon film (having a thickness of 125 nm, for example) and an n⁺ type amorphous silicon film (having a thickness of 65 nm, for example) are formed in this order and patterned to obtain the island-shaped semiconductor layer 5 and the contact layer. The semiconductor film used for the semiconductor layer 5 is not limited to an amorphous silicon film. For example, an oxide semiconductor layer may be formed as the semiconductor layer 5. In this case, it is not necessary to provide a contact layer between the semiconductor layer 5 and the source/drain electrodes.

Next, a source conductive film (having a thickness of greater than or equal to 50 nm and less than or equal to 500 nm, for example) is formed on the gate insulating layer 4 and the contact layer, and is patterned to form a source metal layer including the source electrode 7S, the drain electrode 7D, and the source bus line SL. At this time, the contact layer is also etched, and the source contact layer 6S and the drain contact layer 6D separated from each other are formed.

The material of the source conductive film is not particularly limited to a specific material. A film containing a metal such as aluminum (Al), tungsten (W), molybdenum (Mo), tantalum (Ta), chromium (Cr), titanium (Ti), or copper (Cu), an alloy thereof, or alternatively a metal nitride thereof can be appropriately used. Here, as a source conductive film, a layered film is formed by layering MoN (having a thickness of 30 nm, for example), Al (having a thickness of 200 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order. Or instead, as a source conductive film, a layered film may be formed by layering Ti (having a thickness of 30 nm, for example), MoN (having a thickness of 30 nm, for example), Al (having a thickness of 200 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order.

Here, for example, a source conductive film is formed by a sputtering method and the source conductive film is patterned by wet etching (source/drain separation). Thereafter, a portion of the contact layer located on the region that will serve as the channel region of the semiconductor layer 5 is removed by dry etching, for example, to form a gap portion, and the source contact layer 6S and the drain contact layer 6D are separated. At this time, in the gap portion, the area around the surface of the semiconductor layer 5 is also etched (overetching).

Note that, when a layered film in which a Ti film and an Al film layered in this order is used as a source conductive film, for example, after patterning the Al film by wet etching using, for example, an aqueous solution of phosphoric acid, acetic acid, and nitric acid, the Ti film and the contact layer (n⁺ type amorphous silicon layer) 6 may be simultaneously patterned by dry etching. Alternatively, it is also possible to collectively etch the source conductive film and the contact layer. However, in a case of simultaneously etching the source conductive film, or the lower layer thereof and the contact layer 6, it may be difficult to control the distribution of the etching amount of the semiconductor layer 5 (the amount of excavation of the gap portion) of the entire substrate. In contrast, as described above, in a case where etching is performed in an etching step separate from the source/drain separation and the gap portion formation, the etching amount of the gap portion can be more easily controlled.

Next, the first insulating layer 11 is formed so as to cover the TFT 10. In this example, the first insulating layer 11 is disposed so as to be in contact with the channel region of the semiconductor layer 5. In addition, the contact hole CH1 that at least reaches the drain electrode 7D is formed in the first insulating layer 11 by a known photolithographic method.

The first insulating layer 11 may be an inorganic insulating layer such as a silicon oxide (SiO₂) film, a silicon nitride (SiNx) film, a silicon oxynitride (SiOxNy; x>y) film, or a silicon nitride oxide (SiNxOy; x>y) film, for example. Here, as the first insulating layer 11, a SiNx layer having a thickness of 330 nm, for example, is formed by a CVD method.

Next, a patch conductive film is formed on the first insulating layer 11 and within the contact hole CH1, and this is subsequently patterned. In this way, the patch electrode 15 is formed in the transmission and/or reception region R1, and the patch connection section 15 p is formed in the non-transmission and/or reception region R2. The patch electrode 15 is in contact with the drain electrode 7D within the contact hole CH1. Note that, in the present specification, the layer including the patch electrode 15 and the patch connection section 15 p formed from the patch conductive film may be referred to as a “patch metal layer” in some cases.

The same material as that of the gate conductive film or the source conductive film can be used as the material of the patch conductive film. However, the patch conductive film is set to be thicker than the gate conductive film and the source conductive film. Accordingly, by reducing the sheet resistance of the patch electrode, the loss resulting from the oscillation of free electrons in the patch electrode changing to heat can be reduced. A suitable thickness of the patch conductive film is, for example, greater than or equal to 0.3 μm. In a case where the thickness of the patch conductive film becomes thinner than this, the sheet resistance becomes greater or equal to 0.10 Ω/sq, and there is a possibility that the loss increases. The thickness of the patch conductive film is, for example, less than or equal to 3 μm, and more preferably less than or equal to 2 μm. In a case where the thickness is thicker than this, warping of the substrate may occur. In a case where the warping is large, problems such as conveyance troubles, chipping of the substrate, or cracking of the substrate may occur in the mass production process.

Here, as a patch conductive film, a layered film (MoN/Al/MoN) is formed by layering MoN (having a thickness of 50 nm, for example), Al (having a thickness of 1000 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order. Instead, a layered film (MoN/Al/MoN/Ti) may be formed by layering Ti (having a thickness of 50 nm, for example), MoN (having a thickness of 50 nm, for example), Al (having a thickness of 2000 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order. Alternatively, instead, a layered film (MoN/Al/MoN/Ti) may be formed by layering Ti (having a thickness of 50 nm, for example), MoN (having a thickness of 50 nm, for example), Al (having a thickness of 500 nm, for example), and MoN (having a thickness of 50 nm, for example) in this order. Alternatively, a layered film (Ti/Cu/Ti) in which a Ti film, a Cu film, and a Ti film are layered in this order, or a layered film (Cu/Ti) in which a Ti film and a Cu film are layered in this order may be used.

Next, the second insulating layer (having a thickness of greater than or equal to 100 nm and less than or equal to 300 nm) 17 is formed on the patch electrode 15 and the first insulating layer 11. The second insulating layer 17 is not particularly limited to a specific film, and, for example, a silicon oxide (SiO₂) film, a silicon nitride (SiNx) film, a silicon oxynitride (SiOxNy; x>y) film, a silicon nitride oxide (SiNxOy; x>y) film, or the like can be used as appropriate. Here, as the second insulating layer 17, for example, a SiNx layer having a thickness of 200 nm is formed.

Thereafter, the inorganic insulating films (the second insulating layer 17, the first insulating layer 11, and the gate insulating layer 4) are etched collectively by dry etching using a fluorine-based gas, for example. During the etching, the patch electrode 15, the source bus line SL, and the gate bus line GL each function as an etch stop. In this way, the contact hole CH2 that at least reaches the gate bus line GL is formed in the second insulating layer 17, the first insulating layer 11, and the gate insulating layer 4; and the contact hole CH3 that at least reaches the source bus line SL is formed in the second insulating layer 17 and the first insulating layer 11. In addition, the contact hole CH4 that at least reaches the patch connection section 15 p is formed in the second insulating layer 17.

In this example, since the inorganic insulating films are etched collectively, the side surfaces of the second insulating layer 17, first insulating layer 11, and gate insulating layer 4 are aligned on a side wall of the obtained contact hole CH2, and the side walls of the second insulating layer 17 and first insulating layer 11 are aligned on a side wall of the contact hole CH3. Note that, in the present embodiment, the expression that “the side surfaces of different two or more layers are aligned” within the contact hole does not only refer to when the side surfaces exposed in the contact hole in these layers are flush in the vertical direction, but also includes cases where inclined surfaces such as continuous tapered shapes are formed. Such a structure can be obtained, for example, by etching these layers using the same mask, or alternatively by using one of these layers as a mask to etch the other layer.

Next, a transparent conductive film (having a thickness of greater than or equal to 50 nm and less than or equal to 200 nm) is formed on the second insulating layer 17 and within the contact holes CH2, CH3, and CH4 by a sputtering method, for example. An indium tin oxide (ITO) film, an IZO film, a zinc oxide (ZnO) film or the like can be used as the transparent conductive film. Here, an ITO film having a thickness of, for example, 100 nm is used as the transparent conductive film.

Next, the transparent conductive film is patterned to form the gate terminal upper connection section 19 g, the source terminal upper connection section 19 s, and the transfer terminal upper connection section 19 p. The gate terminal upper connection section 19 g, the source terminal upper connection section 19 s, and the transfer terminal upper connection section 19 p are used for protecting the electrodes or wiring lines exposed at each terminal section. In this way, the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT are obtained.

Structure of Slot Substrate 201

Next, the structure of the slot substrate 201 will be described in greater detail.

FIG. 6 is a cross-sectional view schematically illustrating the antenna unit region U and the terminal section IT in the slot substrate 201.

The slot substrate 201 includes the dielectric substrate 51 having a front surface and a rear surface, a third insulating layer 52 formed on the front surface of the dielectric substrate 51, the slot electrode 55 formed on the third insulating layer 52, and a fourth insulating layer 58 covering the slot electrode 55. The reflective conductive plate 65 is disposed opposing the rear surface of the dielectric substrate 51 with the dielectric layer (air layer) 54 interposed therebetween. The slot electrode 55 and the reflective conductive plate 65 function as the walls of the waveguide 301.

In the transmission and/or reception region R1, the plurality of slots 57 are formed in the slot electrode 55. The slot 57 is an opening that opens through the slot electrode 55. In this example, one slot 57 is disposed in each antenna unit region U.

The fourth insulating layer 58 is formed on the slot electrode 55 and within the slot 57. The material of the fourth insulating layer 58 may be the same as the material of the third insulating layer 52. By covering the slot electrode 55 with the fourth insulating layer 58, the slot electrode 55 and the liquid crystal layer LC are not in direct contact with each other, such that the reliability can be enhanced. In a case where the slot electrode 55 is formed of a Cu layer, Cu may be eluted into the liquid crystal layer LC in some cases. In addition, in a case where the slot electrode 55 is formed of an Al layer by using a thin film deposition technique, the Al layer may include a void. The fourth insulating layer 58 can prevent the liquid crystal material from entering the void of the Al layer. Note that in a case where the slot electrode 55 is formed by bonding an aluminum foil as the Al layer on the dielectric substrate 51 with an adhesive and patterning it, the problem of voids can be avoided.

The slot electrode 55 includes a main layer 55M such as a Cu layer or an Al layer. The slot electrode 55 may have a layered structure that includes the main layer 55M, as well as an upper layer 55U and a lower layer 55L disposed sandwiching the main layer 55M therebetween. A thickness of the main layer 55M may be set in consideration of the skin effect depending on the material, and may be, for example, greater than or equal to 2 μm and less than or equal to 30 μm. The thickness of the main layer 55M is typically greater than the thickness of the upper layer 55U and the lower layer 55L.

In the illustrated example, the main layer 55M is a Cu layer, and the upper layer 55U and the lower layer 55L are Ti layers. By disposing the lower layer 55L between the main layer 55M and the third insulating layer 52, the adhesion between the slot electrode 55 and the third insulating layer 52 can be improved. In addition, by providing the upper layer 55U, corrosion of the main layer 55M (e.g., the Cu layer) can be suppressed.

Since the reflective conductive plate 65 constitutes the wall of the waveguide 301, it is desirable that the reflective conductive plate 65 has a thickness that is three times or greater than the skin depth, and preferably five times or greater. An aluminum plate, a copper plate, or the like having a thickness of several millimeters manufactured by a cutting out process can be used as the reflective conductive plate 65.

The terminal section IT is provided in the non-transmission and/or reception region R2. The terminal section IT includes the slot electrode 55, the fourth insulating layer 58 covering the slot electrode 55, and an upper connection section 60. The fourth insulating layer 58 includes an opening that at least reaches the slot electrode 55. The upper connection section 60 is in contact with the slot electrode 55 within the opening. In the present embodiment, the terminal section IT is disposed in the seal region Rs and is connected to the transfer terminal section on the TFT substrate (transfer section) by a seal resin containing conductive particles.

Transfer Section

FIG. 7 is a schematic cross-sectional view for illustrating the transfer section connecting the transfer terminal section PT of the TFT substrate 101 and the terminal section IT of the slot substrate 201. In FIG. 7, the same reference numerals are attached to the same components as those in FIG. 1 to FIG. 4C.

In the transfer section, the upper connection section 60 of the terminal section IT is electrically connected to the transfer terminal upper connection section 19 p of the transfer terminal section PT in the TFT substrate 101. In the present embodiment, the upper connection section 60 and the transfer terminal upper connection section 19 p are connected with a resin (sealing resin) 73 (also referred to as a sealing portion 73) including conductive beads 71 therebetween.

Each of the upper connection sections 60 and 19 p is a transparent conductive layer such as an ITO film or an IZO film, and there is a possibility that an oxide film is formed on the surface thereof. When an oxide film is formed, the electrical connection between the transparent conductive layers cannot be ensured, and the contact resistance may increase. In contrast, in the present embodiment, since these transparent conductive layers are bonded with a resin including conductive beads (for example, Au beads) 71 therebetween, even in a case where a surface oxide film is formed, the conductive beads pierce (penetrate) the surface oxide film, allowing an increase in contact resistance to be suppressed. The conductive beads 71 may penetrate not only the surface oxide film but also penetrate the upper connection sections 60 and 19 p which are the transparent conductive layers, and directly contact the patch connection section 15 p and the slot electrode 55.

The transfer section may be disposed at both a center portion and a peripheral portion (that is, inside and outside of the donut-shaped transmission and/or reception region R1 when viewed from the normal direction of the scanning antenna 1000) of the scanning antenna 1000, or alternatively may be disposed at only one of them. The transfer section may be disposed in the seal region Rs in which the liquid crystals are sealed, or may be disposed outside the seal region Rs (opposite to the liquid crystal layer).

Manufacturing Method of Slot Substrate 201

The slot substrate 201 can be manufactured by the following method, for example.

First, the third insulating layer (having a thickness of 200 nm, for example) 52 is formed on the dielectric substrate. A substrate such as a glass substrate or a resin substrate having a high transmittance to electromagnetic waves (the dielectric constant ε_(M) and the dielectric loss tan δ_(M) are small) can be used as the dielectric substrate. The dielectric substrate is preferably thin in order to suppress the attenuation of the electromagnetic waves. For example, after forming the constituent elements such as the slot electrode 55 on the front surface of the glass substrate by a process to be described later, the glass substrate may be thinned from the rear side. This allows the thickness of the glass substrate to be reduced to 500 μm or less, for example.

When a resin substrate is used as the dielectric substrate, constituent elements such as TFTs may be formed directly on the resin substrate, or may be formed on the resin substrate by a transfer method. In a case of the transfer method, for example, a resin film (for example, a polymide film) is formed on the glass substrate, and after the constituent elements are formed on the resin film by the process to be described later, the resin film on which the constituent elements are formed is separated from the glass substrate. Generally, the dielectric constant ε_(M) and the dielectric loss tan δ_(M) of resin are smaller than those of glass. The thickness of the resin substrate is, for example, from 3 μm to 300 μm. Besides polyimide, for example, a liquid crystal polymer can also be used as the resin material.

The third insulating layer 52 is not particularly limited to a specific film, and, for example, a silicon oxide (SiO₂) film, a silicon nitride (SiNx) film, a silicon oxynitride (SiOxNy; x>y) film, a silicon nitride oxide (SiNxOy; x>y) film, or the like can be used as appropriate.

Next, a metal film is formed on the third insulating layer 52, and this is patterned to obtain the slot electrode 55 including the plurality of slots 57. As the metal film, a Cu film (or Al film) having a thickness of from 2 μm to 5 μm may be used. Here, a layered film obtained by layering a Ti film, a Cu film, and a Ti film in this order is used. Instead, a layered film may be formed by layering Ti (having a thickness of 50 nm, for example) and Cu (having a thickness of 5000 nm, for example) in this order.

Thereafter, the fourth insulating layer (having a thickness of 100 nm or 200 nm, for example) 58 is formed on the slot electrode 55 and within the slot 57. The material of the fourth insulating layer 58 may be the same as the material of the third insulating layer. Subsequently, in the non-transmission and/or reception region R2, an opening that at least reaches the slot electrode 55 is formed in the fourth insulating layer 58.

Next, a transparent conductive film is formed on the fourth insulating layer 58 and within the opening of the fourth insulating layer 58, and is patterned to form the upper connection section 60 in contact with the slot electrode 55 within the opening. In this way, the terminal section IT is obtained.

Material and Structure of TFT 10

In the present embodiment, a TFT including a semiconductor layer 5 as an active layer is used as a switching element disposed in each pixel. The semiconductor layer 5 is not limited to an amorphous silicon layer, and may be a polysilicon layer or an oxide semiconductor layer.

In a case where an oxide semiconductor layer is used, the oxide semiconductor included in the oxide semiconductor layer may be an amorphous oxide semiconductor or a crystalline oxide semiconductor including a crystalline portion. Examples of the crystalline oxide semiconductor include a polycrystalline oxide semiconductor, a microcrystalline oxide semiconductor, or a crystalline oxide semiconductor having a c-axis oriented substantially perpendicular to the layer surface.

The oxide semiconductor layer may have a layered structure of two or more layers. In a case where the oxide semiconductor layer has a layered structure, the oxide semiconductor layer may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer. Alternatively, the oxide semiconductor layer may include a plurality of crystalline oxide semiconductor layers having different crystal structures. In addition, the oxide semiconductor layer may include a plurality of amorphous oxide semiconductor layers. In a case where the oxide semiconductor layer has a two-layer structure including an upper layer and a lower layer, the energy gap of the oxide semiconductor included in the upper layer is preferably greater than the energy gap of the oxide semiconductor included in the lower layer. However, when the difference in the energy gap between these layers is relatively small, the energy gap of the lower layer oxide semiconductor may be greater than the energy gap of the upper layer oxide semiconductor.

JP 2014-007399 A, for example, describes the materials, structures, film formation methods, and configuration of oxide semiconductor layers having layered structures for amorphous oxide semiconductors and each of the above described crystalline oxide semiconductors. For reference, the entire content of JP 2014-007399 A is incorporated herein.

The oxide semiconductor layer may include, for example, at least one metal element selected from In, Ga, and Zn. In the present embodiment, the oxide semiconductor layer includes, for example, an In—Ga—Zn—O based semiconductor (for example, indium gallium zinc oxide). Here, the In—Ga—Zn—O based semiconductor is a ternary oxide of In (indium), Ga (gallium), and Zn (zinc), and the ratio (composition ratio) of In, Ga, and Zn is not particularly limited to a specific value. For example, the ratio includes In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, or In:Ga:Zn=1:1:2. Such an oxide semiconductor layer can be formed from an oxide semiconductor film including an In—Ga—Zn—O based semiconductor.

The In—Ga—Zn—O based semiconductor may be an amorphous semiconductor or a crystalline semiconductor. A crystalline In—Ga—Zn—O based semiconductor in which the c-axis is oriented substantially perpendicular to the layer surface is preferable as the crystalline In—Ga—Zn—O based semiconductor.

Note that the crystal structure of the crystalline In—Ga—Zn—O based semiconductor is disclosed in, for example, the above-mentioned JP 2014-007399 A, JP 2012-134475 A, and JP 2014-209727 A. For reference, the entire content of JP 2012-134475 A and 2014-209727 A is incorporated herein. Since a TFT including an In—Ga—Zn—O based semiconductor layer has high mobility (more than 20 times in comparison with a-Si TFTs) and low leakage current (less than 1/100th in comparison with a-Si TFTs), such a TFT can suitably be used as a driving TFT (for example, a TFT included in a driving circuit provided in the non-transmission and/or reception region) and a TFT provided in each antenna unit region.

In place of the In—Ga—Zn—O based semiconductor, the oxide semiconductor layer may include another oxide semiconductor. For example, the oxide semiconductor layer may include an In—Sn—Zn—O based semiconductor (for example, In₂O₃—SnO₂—ZnO; InSnZnO). The In—Sn—Zn—O based semiconductor is a ternary oxide of In (indium), Sn (tin), and Zn (zinc). Alternatively, the oxide semiconductor layer may include an In—Al—Zn—O based semiconductor, an In—Al—Sn—Zn—O based semiconductor, a Zn—O based semiconductor, an In—Zn—O based semiconductor, a Zn—Ti—O based semiconductor, a Cd—Ge—O based semiconductor, a Cd—Pb—O based semiconductor, CdO (cadmium oxide), a Mg—Zn—O based semiconductor, an In—Ga—Sn—O based semiconductor, an In—Ga—O based semiconductor, a Zr—In—Zn—O based semiconductor, an Hf—In—Zn—O based semiconductor, an Al—Ga—Zn—O based semiconductor, or a Ga—Zn—O based semiconductor.

In the example illustrated in FIG. 3A and FIG. 3B, the TFT 10 is a channel etch type TFT having a bottom gate structure. The channel etch type TFT does not include an etch stop layer formed on the channel region, and a lower face of an end portion of each of the source and drain electrodes, which is closer to the channel, is provided so as to be in contact with an upper face of the semiconductor layer. The channel etch type TFT is formed by, for example, forming a conductive film for a source/drain electrode on a semiconductor layer and performing source/drain separation. In the source/drain separation process, the surface portion of the channel region may be etched.

Note that the TFT 10 may be an etch stop type TFT in which an etch stop layer is formed on the channel region. In the etch stop type TFT, the lower face of an end portion of each of the source and drain electrodes, which is closer to the channel, is located, for example, on the etch stop layer. The etch stop type TFT is formed as follows; after forming an etch stop layer covering the portion that will become the channel region in a semiconductor layer, for example, a conductive film for the source and drain electrodes is formed on the semiconductor layer and the etch stop layer, and source/drain separation is performed.

In addition, although the TFT 10 has a top contact structure in which the source and drain electrodes are in contact with the upper face of the semiconductor layer, the source and drain electrodes may be disposed to be in contact with the lower face of the semiconductor layer (a bottom contact structure). Furthermore, the TFT 10 may have a bottom gate structure having a gate electrode on the dielectric substrate side of the semiconductor layer, or a top gate structure having a gate electrode above the semiconductor layer.

Second Embodiment

The scanning antenna of a second embodiment will be described with reference to drawings. The TFT substrate of the scanning antenna of the present embodiment differs from the TFT substrate 101 illustrated in FIG. 2A in that a transparent conductive layer that serves as an upper connection section for each terminal section is provided between the first insulating layer and the second insulating layer of the TFT substrate.

FIG. 8A to FIG. 8C are cross-sectional views illustrating the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT, respectively, of a TFT substrate 102 in the present embodiment. Constituent elements similar to those in FIG. 4A to FIG. 4C are denoted by the same reference numerals, and the description thereof is omitted. Since the cross-sectional structure of the antenna unit region U is similar to that of the above-described embodiments (FIG. 3A and FIG. 3B), the illustration and description thereof will be omitted.

The gate terminal section GT in the present embodiment includes the gate bus line GL formed on a dielectric substrate, the insulating layer covering the gate bus line GL, and the gate terminal upper connection section 19 g. The gate terminal upper connection section 19 g is in contact with the gate bus line GL within the contact hole CH2 formed in the insulating layer. In this example, the insulating layer covering the gate bus line GL includes the gate insulating layer 4 and the first insulating layer 11. The second insulating layer 17 is formed on the gate terminal upper connection section 19 g and the first insulating layer 11. The second insulating layer 17 includes an opening 18 g exposing a part of the gate terminal upper connection section 19 g. In this example, the opening 18 g of the second insulating layer 17 may be disposed so as to expose the entire contact hole CH2.

The source terminal section ST includes the source bus line SL formed on the dielectric substrate (here, on the gate insulating layer 4), the insulating layer covering the source bus line SL, and the source terminal upper connection section 19 s. The source terminal upper connection section 19 s is in contact with the source bus line SL within the contact hole CH3 formed in the insulating layer. In this example, the insulating layer covering the source bus line SL includes only the first insulating layer 11. The second insulating layer 17 extends over the source terminal upper connection section 19 s and the first insulating layer 11. The second insulating layer 17 includes an opening 18 s exposing a part of the source terminal upper connection section 19 s. The opening 18 s of the second insulating layer 17 may be disposed so as to expose the entire contact hole CH3.

The transfer terminal section PT includes a source connection wiring line 7 p formed from the same conductive film (source conductive film) as that of the source bus line SL, the first insulating layer 11 extending over the source connection wiring line 7 p, and the transfer terminal upper connection section 19 p and the patch connection section 15 p formed on the first insulating layer 11.

Contact holes CH5 and CH6 are provided in the first insulating layer 11 to expose the source connection wiring line 7 p. The transfer terminal upper connection section 19 p is disposed on the first insulating layer 11 and within the contact hole CH5, and is in contact with the source connection wiring line 7 p within the contact hole CH5. The patch connection section 15 p is disposed on the first insulating layer 11 and within the contact hole CH6, and is in contact with the source connection wiring line 7 p within the contact hole CH6. The transfer terminal upper connection section 19 p is a transparent electrode formed of a transparent conductive film. The patch connection section 15 p is formed of the same conductive film as that of the patch electrode 15. Note that the upper connection sections 19 g, 19 s, and 19 p of the respective terminal sections may be formed of the same transparent conductive film.

The second insulating layer 17 extends over the transfer terminal upper connection section 19 p, the patch connection section 15 p, and the first insulating layer 11. The second insulating layer 17 includes an opening 18 p exposing a part of the transfer terminal upper connection section 19 p. In this example, the opening 18 p of the second insulating layer 17 is disposed so as to expose the entire contact hole CH5. In contrast, the patch connection section 15 p is covered with the second insulating layer 17.

In this way, in the present embodiment, the source connection wiring line 7 p formed in the source metal layer electrically connects the transfer terminal upper connection section 19 p of the transfer terminal section PT and the patch connection section 15 p. Although not illustrated in drawings, similar to the above-described embodiment, the transfer terminal upper connection section 19 p is connected to the slot electrode of the slot substrate 201 by a sealing resin containing conductive particles.

In the previously described embodiment, the contact holes CH1 to CH4 having different depths are collectively formed after the formation of the second insulating layer 17. For example, while the relatively thick insulating layers (the gate insulating layer 4, the first insulating layer 11 and the second insulating layer 17) are etched in the gate terminal section GT, only the second insulating layer 17 is etched in the transfer terminal section PT. Accordingly, there is a possibility that the conductive film (for example, a patch electrode conductive film) that serves as the base of the shallow contact holes is considerably damaged during etching.

In contrast, in the present embodiment, the contact holes CH1 to CH3, CH5, and CH6 are formed prior to the formation of the second insulating layer 17. Since these contact holes are formed only in the first insulating layer 11 or in the layered film of the first insulating layer 11 and the gate insulating layer 4, the difference in the depth of the collectively formed contact holes can be reduced more than in the previous embodiment. Accordingly, the damage to the conductive film that serves as the base of the contact holes can be reduced. In particular, when an Al film is used for the patch electrode conductive film, since a favorable contact cannot be obtained in a case where the ITO film and the Al film are brought into direct contact with each other, a cap layer such as a MoN layer may be formed on the Al film in some cases. In these cases, there is the advantage that the thickness of the cap layer does not need to be increased to compensate for the damage during etching.

Manufacturing Method of TFT Substrate 102

The TFT substrate 102 is manufactured by the following method, for example. FIG. 9 is a diagram illustrating an example of a manufacturing process of the TFT substrate 102. Note that in the following description, in cases where the material, thickness, formation method, or the like of each layer are the same as that of the TFT substrate 101 described above, the description thereof is omitted.

First, an alignment mark, a base insulating layer, a gate metal layer, a gate insulating layer, a semiconductor layer, a contact layer, and a source metal layer are formed on a dielectric substrate in the same manner as in the TFT substrate 101 to obtain a TFT. In the step of forming the source metal layer, in addition to the source and drain electrodes and the source bus line, the source connection wiring line 7 p is also formed from the source conductive film.

Next, the first insulating layer 11 is formed so as to cover the source metal layer. Subsequently, the first insulating layer 11 and the gate insulating layer 4 are collectively etched to form the contact holes CH1 to CH3, CH5, and CH6. During etching, each of the source bus line SL and the gate bus line GL functions as an etch stop. In this way, in the transmission and/or reception region R1, the contact hole CH1 that at least reaches the drain electrode of the TFT is formed in the first insulating layer 11. In addition, in the non-transmission and/or reception region R2, the contact hole CH2 that at least reaches the gate bus line GL is formed in the first insulating layer 11 and the gate insulating layer 4, and the contact hole CH3 that at least reaches the source bus line SL and contact holes CH5 and CH6 that at least reach the source connection wiring line 7 p are formed in the first insulating layer 11. The contact hole CH5 may be disposed in the seal region Rs and the contact hole CH6 may be disposed outside the seal region Rs. Alternatively, both may be disposed outside the seal region Rs.

Next, a transparent conductive film is formed on the first insulating layer 11 and within the contact holes CH1 to CH3, CH5, and CH6, and patterned. In this way, the gate terminal upper connection section 19 g in contact with the gate bus line GL within the contact hole CH2, the source terminal upper connection section 19 s in contact with the source bus line SL within the contact hole CH3, and the transfer terminal upper connection section 19 p in contact with the source connection wiring line 7 p within the contact hole CH5 are formed.

Next, a patch electrode conductive film is formed on the first insulating layer 11, the gate terminal upper connection section 19 g, the source terminal upper connection section 19 s, the transfer terminal upper connection section 19 p, and within the contact holes CH1 and CH6 and patterned. In this way, the patch electrode 15 in contact with the drain electrode 7D within the contact hole CH1 is formed in the transmission and/or reception region R1; and the patch connection section 15 p in contact with the source connection wiring line 7 p within the contact hole CH6 is formed in the non-transmission and/or reception region R2. Patterning of the patch electrode conductive film may be performed by wet etching. Here, an etchant capable of increasing the etching selection ratio between the transparent conductive film (ITO or the like) and the patch electrode conductive film (for example, an Al film) is used. In this way, when patterning the patch electrode conductive film, the transparent conductive film can function as an etch stop. Since the portions of the source bus line SL, the gate bus line GL, and the source connection wiring line 7 p exposed by the contact holes CH2, CH3, and CH5 are covered with an etch stop (transparent conductive film), they are not etched.

Subsequently, the second insulating layer 17 is formed. Thereafter, the second insulating layer 17 is patterned by, for example, dry etching using a fluorine-based gas. In this way, the opening 18 g exposing the gate terminal upper connection section 19 g, the opening 18 s exposing the source terminal upper connection section 19 s, and the opening 18 p exposing the transfer terminal upper connection section 19 p are provided in the second insulating layer 17. In this manner, the TFT substrate 102 is obtained.

Third Embodiment

The scanning antenna of a third embodiment will be described with reference to drawings. The TFT substrate in the scanning antenna of the present embodiment differs from the TFT substrate 102 illustrated in FIGS. 8A to 8C in that the upper connection section made of a transparent conductive film is not provided in the transfer terminal section.

FIG. 10A to FIG. 10C are cross-sectional views illustrating the gate terminal section GT, the source terminal section ST, and the transfer terminal section PT, respectively, of a TFT substrate 103 in the present embodiment. Constituent elements similar to those in FIG. 8A to FIG. 8C are denoted by the same reference numerals. Since the structure of the antenna unit region U is similar to that of the above-described embodiments (FIG. 3A and FIG. 3B), the illustration and description thereof will be omitted.

The structures of the gate terminal section GT and the source terminal section ST are similar to the structures of the gate terminal section and the source terminal section of the TFT substrate 102 illustrated in FIG. 8A and FIG. 8B.

The transfer terminal section PT includes the patch connection section 15 p formed on the first insulating layer 11 and a protective conductive layer 23 layered on the patch connection section 15 p. The second insulating layer 17 extends over the protective conductive layer 23 and includes an opening 18 p exposing a part of the protective conductive layer 23. In contrast, the patch electrode 15 is covered with the second insulating layer 17.

Manufacturing Method of TFT Substrate 103

The TFT substrate 103 is manufactured by the following method, for example. FIG. 11 is a diagram illustrating an example of a manufacturing process of the TFT substrate 103. Note that in the following description, in cases where the material, thickness, formation method, or the like of each layer are the same as that of the TFT substrate 101 described above, the description thereof is omitted.

First, an alignment mark, a base insulating layer, a gate metal layer, a gate insulating layer, a semiconductor layer, a contact layer, and a source metal layer are formed on a dielectric substrate in the same manner as in the TFT substrate 101 to obtain a TFT.

Next, the first insulating layer 11 is formed so as to cover the source metal layer. Subsequently, the first insulating layer 11 and the gate insulating layer 4 are collectively etched to form the contact holes CH1 to CH3. During etching, each of the source bus line SL and the gate bus line GL functions as an etch stop. In this way, the contact hole CH1 that at least reaches the drain electrode of the TFT is formed in the first insulating layer 11, the contact hole CH2 that at least reaches the gate bus line GL is formed in the first insulating layer 11 and the gate insulating layer 4, and the contact hole CH3 that at least reaches the source bus line SL is formed in the first insulating layer 11. No contact hole is formed in the region where the transfer terminal section is formed.

Next, a transparent conductive film is formed on the first insulating layer 11 and within the contact holes CH1, CH2, and CH3, and patterned. In this way, the gate terminal upper connection section 19 g in contact with the gate bus line GL within the contact hole CH2 and the source terminal upper connection section 19 s in contact with the source bus line SL within the contact hole CH3 are formed. In the region where the transfer terminal section is formed, the transparent conductive film is removed.

Next, a patch electrode conductive film is formed on the first insulating layer 11, on the gate terminal upper connection section 19 g and the source terminal upper connection section 19 s, and within the contact hole CH1, and patterned. In this way, the patch electrode 15 in contact with the drain electrode 7D within the contact hole CH1 is formed in the transmission and/or reception region R1, and the patch connection section 15 p is formed in the non-transmission and/or reception region R2. Similar to the previous embodiments, an etchant capable of ensuring an etching selection ratio between the transparent conductive film (ITO or the like) and the patch electrode conductive film is used for patterning the patch electrode conductive film.

Subsequently, the protective conductive layer 23 is formed on the patch connection section 15 p. A Ti layer, an ITO layer, and an indium zinc oxide (IZO) layer (having a thickness of greater than or equal to 50 nm and less than or equal to 100 nm, for example), or the like can be used as the protective conductive layer 23. Here, a Ti layer (having a thickness of 50 nm, for example) is used as the protective conductive layer 23. Note that the protective conductive layer may be formed on the patch electrode 15.

Next, the second insulating layer 17 is formed. Thereafter, the second insulating layer 17 is patterned by, for example, dry etching using a fluorine-based gas. In this way, the opening 18 g exposing the gate terminal upper connection section 19 g, the opening 18 s exposing the source terminal upper connection section 19 s, and the opening 18 p exposing the protective conductive layer 23 are provided in the second insulating layer 17. In this manner, the TFT substrate 103 is obtained.

Structure of Slot Substrate 203

FIG. 12 is a schematic cross-sectional view for illustrating a transfer section that connects the transfer terminal section PT of the TFT substrate 103 and a terminal section IT of a slot substrate 203 in the present embodiment. In FIG. 12, the same reference numerals are attached to the same constituent elements as those in the embodiments described above.

First, the slot substrate 203 in this embodiment will be described. The slot substrate 203 includes the dielectric substrate 51, the third insulating layer 52 formed on the front surface of the dielectric substrate 51, the slot electrode 55 formed on the third insulating layer 52, and the fourth insulating layer 58 covering the slot electrode 55. The reflective conductive plate 65 is disposed opposing the rear surface of the dielectric substrate 51 with the dielectric layer (air layer) 54 interposed therebetween. The slot electrode 55 and the reflective conductive plate 65 function as the walls of the waveguide 301.

The slot electrode 55 has a layered structure in which a Cu layer or an Al layer is the main layer 55M. In the transmission and/or reception region R1, the plurality of slots 57 are formed in the slot electrode 55. The structure of the slot electrode 55 in the transmission and/or reception region R1 is the same as the structure of the slot substrate 201 described above with reference to FIG. 6.

The terminal section IT is provided in the non-transmission and/or reception region R2. The terminal section IT includes an opening exposing the front surface of the slot electrode 55 provided in the fourth insulating layer 58. The exposed area of the slot electrode 55 serves as a contact surface 55 c. As described above, in the present embodiment, the contact surface 55 c of the slot electrode 55 is not covered with the fourth insulating layer 58.

In the transfer section, the protective conductive layer 23 covering the patch connection section 15 p of the TFT substrate 103 and the contact surface 55 c of the slot electrode 55 of the slot substrate 203 are connected with a resin (sealing resin) containing the conductive beads 71 therebetween.

As in the above-described embodiments, the transfer section in the present embodiment may be disposed at both the central portion and the peripheral portion of the scanning antenna, or may be disposed in only one of them. In addition, the transfer section may be disposed within the seal region Rs or may be disposed outside the seal region Rs (opposite to the liquid crystal layer).

In the present embodiment, no transparent conductive film is provided on the transfer terminal PT and the contact surface of the terminal section IT. Accordingly, the protective conductive layer 23 and the slot electrode 55 of the slot substrate 203 can be connected with a sealing resin containing conductive particles therebetween.

Furthermore, in the present embodiment, since the difference in the depth of the collectively formed contact holes is small in comparison with the first embodiment (FIG. 3A to FIG. 4C), the damage to the conductive film that serves as the base of the contact holes can be reduced.

Manufacturing Method of Slot Substrate 203

The slot substrate 203 is manufactured as follows. Since the material, the thickness, and the formation method of each layer are the same as those of the slot substrate 201, the description thereof is omitted.

First, the third insulating layer 52 and the slot electrode 55 are formed on the dielectric substrate in the same manner as the slot substrate 201, and the plurality of slots 57 are formed in the slot electrode 55. Next, the fourth insulating layer 58 is formed on the slot electrode 55 and within the slot. Subsequently, the opening 18 p is formed in the fourth insulating layer 58 so as to expose a region that will become the contact surface of the slot electrode 55. In this way, the slot substrate 203 is manufactured.

Internal Heater Structure

As described above, it is preferable that the dielectric anisotropy Δε_(M) of the liquid crystal material used for the antenna units of the antenna be large. However, the viscosity of liquid crystal materials (nematic liquid crystals) having large dielectric anisotropies Δε_(M) is high, and the slow response speed may lead to problems. In particular, as the temperature decreases, the viscosity increases. The environmental temperature of a scanning antenna mounted on a moving body (for example, a ship, an aircraft, or an automobile) fluctuates. Accordingly, it is preferable that the temperature of the liquid crystal material can be adjusted to a certain extent, such as 30° C. or higher, or 45° C. or higher, for example. The set temperature is preferably set such that the viscosity of the nematic liquid crystal material is about 10 cP (centipoise) or less.

In addition to the above structure, the scanning antenna according to the embodiments of the disclosure preferably has an internal heater structure. A resistance heating type heater that uses Joule heat is preferable as the internal heater. The material of the resistive film for the heater is not particularly limited to a specific material, but a conductive material having relatively high specific resistance such as ITO or IZO can be utilized, for example. In addition, to adjust the resistance value, a resistive film may be formed with thin lines or meshes made of a metal (e.g., nichrome, titanium, chromium, platinum, nickel, aluminum, and copper). Thin lines or meshes made of ITO and IZO may be also used. The resistance value may be set according to the required calorific value.

For example, to set the heat generation temperature of the resistive film to 30° C. for an area (roughly 90000 mm²) of a circle having a diameter of 340 mm with 100 V AC (60 Hz), the resistance value of the resistive film should be set to 139Ω, the current should be set to 0.7 A, and the power density should be set to 800 W/m². To set the heat generation temperature of the resistive film to 45° C. for the same area with 100 V AC (60 Hz), the resistance value of the resistive film should be set to 82Ω, the current should be set to 1.2 A, and the power density should be set to 1350 W/m².

The resistive film for the heater may be provided anywhere as long as it does not affect the operation of the scanning antenna, but to efficiently heat the liquid crystal material, the resistive film is preferably provided near the liquid crystal layer. For example, as illustrated in a TFT substrate 104 illustrated in FIG. 13A, a resistive film 68 may be formed on almost the entire surface of the dielectric substrate 1. FIG. 13A is a schematic plan view of the TFT substrate 104 including the heater resistive film 68. The resistive film 68 is covered with, for example, the base insulating film 2 illustrated in FIG. 3A. The base insulating film 2 is formed to have a sufficient dielectric strength.

The resistive film 68 preferably has openings 68 a, 68 b, and 68 c. When the TFT substrate 104 and the slot substrate are bonded to each other, the slots 57 are positioned to oppose the patch electrodes 15. At this time, the opening 68 a is disposed such that the resistive film 68 is not present within an area having a distance d from an edge of the slot 57. The distance d is 0.5 mm, for example. In addition, it is also preferable to dispose the opening 68 b under the auxiliary capacitance CS and to dispose the opening portion 68 c under the TFT.

Note that the size of the antenna unit U is, for example, 4 mm×4 mm. In addition, as illustrated in FIG. 13B, a width s2 of the slot 57 is 0.5 mm, a length s1 of the slot 57 is 3.3 mm, a width p2 of the patch electrode 15 in a width direction of the slot 57 is 0.7 mm, and a width p1 of the patch electrode 15 in the length direction of the slot 57 is 0.5 mm. Note that the size, shape, arrangement relationships, and the like of the antenna unit U, the slot 57, and the patch electrode 15 are not limited to the examples illustrated in FIG. 13A and FIG. 13B.

To further reduce the influence of the electric field from the heater resistive film 68, a shield conductive layer may be formed. The shield conductive layer is formed, for example, on the base insulating film 2 over almost the entire surface of the dielectric substrate 1. While the shield conductive layer does not need to include the openings 68 a and 68 b like in the resistive film 68, the opening 68 c is preferably provided therein. The shield conductive layer is formed of, for example, an aluminum layer, and is set to a ground potential.

In addition, the resistive film preferably has a distribution of the resistance value so that the liquid crystal layer can be uniformly heated. A temperature distribution of the liquid crystal layer is preferably such that the difference between the maximum temperature and the minimum temperature (temperature fluctuation) is, for example, less than or equal to 15° C. When the temperature fluctuation exceeds 15° C., there are cases that the phase difference modulation varies within the plane, and a problem may occur in which good quality beam formation cannot be achieved. Furthermore, when the temperature of the liquid crystal layer approaches the Tni point (for example, 125° C.), Δε_(M) becomes small, which is not preferable.

With reference to FIG. 14A, FIG. 14B, and FIG. 15A to FIG. 15C, the distribution of the resistance value in the resistive film will be described. FIG. 14A, FIG. 14B, and FIG. 15A to FIG. 15C illustrate the schematic structures of resistance heating structures 80 a to 80 e and a current distribution. The resistance heating structure includes a resistive film and a heater terminal.

The resistance heating structure 80 a illustrated in FIG. 14A includes a first terminal 82 a, a second terminal 84 a, and a resistive film 86 a connected thereto. The first terminal 82 a is disposed at the center of the circle, and the second terminal 84 a is disposed along the entire circumference. Here, the circle corresponds to the transmission and/or reception region R1. When a DC voltage is applied between the first terminal 82 a and the second terminal 84 a, for example, a current IA flows radially from the first terminal 82 a to the second terminal 84 a. Accordingly, even though an in-plane resistance value is constant, the resistive film 86 a can uniformly generate heat. Of course, the direction of a current flow may be a direction from the second terminal 84 a to the first terminal 82 a.

The resistance heating structure 80 b illustrated in FIG. 14B includes a first terminal 82 b, a second terminal 84 b, and a resistive film 86 b connected thereto. The first terminal 82 b and the second terminal 84 b are disposed adjacent to each other along the circumference. A resistance value of the resistive film 86 b has an in-plane distribution such that an amount of heat generated per unit area by the current IA flowing between the first terminal 82 b and the second terminal 84 b in the resistive film 86 b is constant. In a case where the resistive film 86 b is formed in a thin line, for example, the in-plane distribution of the resistance value of the resistive film 86 may be adjusted by the thickness of the thin line and the density of the thin line.

The resistance heating structure 80 c illustrated in FIG. 15A includes a first terminal 82 c, a second terminal 84 c, and a resistive film 86 c connected thereto. The first terminal 82 c is disposed along the circumference of the upper half of the circle, and the second terminal 84 c is disposed along the circumference of the lower half of the circle. When the resistive film 86 c is constituted by thin lines extending vertically between the first terminal 82 c and the second terminal 84 c, for example, a thickness and a density of the thin lines near the center are adjusted such that the amount of heat generated per unit area by the current IA is constant in the plane.

The resistance heating structure 80 d illustrated in FIG. 15B includes a first terminal 82 d, a second terminal 84 d, and a resistive film 86 d connected thereto. The first terminal 82 d and the second terminal 84 d are provided so as to extend in the vertical direction and the horizontal direction, respectively, along the diameter of the circle. Although simplified in drawings, the first terminal 82 d and the second terminal 84 d are electrically insulated from each other.

In addition, the resistance heating structure 80 e illustrated in FIG. 15C includes a first terminal 82 e, a second terminal 84 e, and a resistive film 86 e connected thereto. Unlike the resistance heating structure 80 d, both of the first terminal 82 e and the second terminal 84 e of the resistance heating structure 80 e include four portions extending from the center of the circle in four directions upward, downward, left, and right. The portions of the first terminal 82 e and the second terminal 84 e that form a 90 degree angle with each other are disposed such that the current IA flows clockwise.

In both of the resistance heating structure 80 d and the resistance heating structure 80 e, the thin line closer to the circumference is adjusted to be thick and have a higher density, for example, so that the closer to the circumference the more the current IA increases, and the amount of heat generated per unit area becomes uniform within the plane.

Such an internal heater structure may automatically operate, for example, when it is detected that the temperature of the scanning antenna has fallen below a preset temperature. Of course, it may also operate in response to the user operation.

External Heater Structure

Instead of the internal heater structure described above, or in addition to the internal heater structure, the scanning antenna according to the embodiments of the disclosure may include an external heater structure. A resistance heating type heater that uses Joule heat is preferable as the external heater although various known heaters can be used. Assume that a part generating heat in the heater is a heater section. In the following description, an example in which a resistive film is used as the heater section is described. In the following description also, the resistive film is denoted by the reference numeral 68.

For example, the heater resistive film 68 is preferably disposed as in a liquid crystal panel 100Pa or 100Pb illustrated in FIGS. 16A and 16B. Here, the liquid crystal panels 100Pa and 100Pb includes the TFT substrate 101, the slot substrate 201, and the liquid crystal layer LC provided therebetween in the scanning antenna 1000 illustrated in FIG. 1, and further includes a resistance heating structure including the resistive film 68 on an outer side of the TFT substrate 101. The resistive film 68 may be formed on a side of the dielectric substrate 1 of the TFT substrate 101 closer to the liquid crystal layer LC. However, such a configuration complicates a manufacturing process of the TFT substrate 101, and thus the resistive film 68 is preferably disposed on the outer side of the TFT substrate 101 (opposite to the liquid crystal layer LC).

The liquid crystal panel 100Pa illustrated in FIG. 16A includes the heater resistive film 68 formed on an outer surface of the dielectric substrate 1 of the TFT substrate 101 and a protection layer 69 a covering the heater resistive film 68. The protection layer 69 a may be omitted. The scanning antenna is housed in a case made of plastic, for example, and therefore, the resistive film 68 is not directly contacted by the user.

The resistive film 68 can be formed on the outer surface of the dielectric substrate 1 by the use of, for example, a known thin film deposition technique (e.g., sputtering, CVD), a coating method, or a printing method. The resistive film 68 is patterned as needed. Patterning is performed through a photolithographic process, for example.

The material of the heater resistive film 68 is not particularly limited to a specific material as described above for the internal heater structure, but a conductive material having relatively high specific resistance such as ITO or IZO can be utilized, for example. In addition, to adjust the resistance value, the resistive film 68 may be formed in thin lines or meshes made of a metal (e.g., nichrome, titanium, chromium, platinum, nickel, aluminum, and copper). Thin lines or meshes made of ITO and IZO may be also used. The resistance value may be set according to the required calorific value.

The protection layer 69 a is made of an insulating material and formed to cover the resistive film 68. The protection layer 69 a may not be formed on a portion where the resistive film 68 is patterned and the dielectric substrate 1 is exposed. The resistive film 68 is patterned so as not to decrease the antenna performance as described later. In a case where a presence of the material forming the protection layer 69 a causes the antenna performance to decrease, the patterned protection layer 69 a is preferably used similar to the resistive film 68.

The protection layer 69 a may be formed by any of a wet process and a dry process. For example, a liquid curable resin (or precursor of resin) or a solution is applied to the surface of the dielectric substrate 1 on which the resistive film 68 is formed, and thereafter, the curable resin is cured to form the protection layer 69 a. The liquid resin or the resin solution is applied to the surface of the dielectric substrate 1 to have a predetermined thickness by various coating methods (e.g., using a slot coater, a spin coater, or a spray) or various printing methods. After that, the resultant substrate is subjected to room temperature curing, thermal curing, or light curing depending on a kind of the resin to form the protection layer 69 a which is an insulating resin film. The insulating resin film may be patterned by a photolithographic process, for example.

A curable resin material is preferably used as a material for forming the protection layer 69 a. The curable resin material includes a thermal curing type resin material and a light curing type resin material. The thermal curing type includes a thermal cross-linking type and a thermal polymerization type.

Examples of the resin material of thermal cross-linking type include a combination of an epoxy-based compound (e.g., an epoxy resin) and amine-based compound, a combination of an epoxy-based compound and a hydrazide-based compound, a combination of an epoxy-based compound and an alcohol-based compound (e.g., including a phenol resin), a combination of an epoxy-based compound and a carboxylic acid-based compound (e.g., including an acid anhydride), a combination of an isocyanate-based compound and an amine-based compound, a combination of an isocyanate-based compound and a hydrazide-based compound, a combination of an isocyanate-based compound and an alcohol-based compound (e.g., including an urethane resin), and a combination of an isocyanate-based compound and a carboxylic acid-based compound. Examples of a cationic polymerization type adhesive include a combination of an epoxy-based compound and a cationic polymerization initiator (a representative cationic polymerization initiator: aromatic sulfonium salt). Examples of the resin material of radical polymerization type include a combination of a monomer and/or an oligomer containing a vinyl group of various acrylic, methacrylic, and urethane modified acrylic (methacrylic) resins and a radical polymerization initiator (a representative radical polymerization initiator: azo-based compound (e.g., azobisisobutyronitrile (AIBN))), and examples of the resin material of ring-opening polymerization type include an ethylene oxide-based compound, an ethyleneimine-based compound, and a siloxane-based compound. In addition, examples of the resin material may also include a maleimide resin, a combination of a maleimide resin and an amine, a combination of maleimide and a methacrylic compound, a bismaleimide-triazine resin, and a polyphenylene ether resin. Moreover, polyimide can be preferably used. Note that “polyimide” including polyamic acid that is a precursor of polyimide is used. Polyimide is used in combination with an epoxy-based compound or an isocyanate-based compound, for example.

In terms of a heat resistance, a chemical stability, and mechanical characteristics, the thermal curing type resin material is preferably used. Particularly, the resin material containing an epoxy resin or a polyimide resin is preferable, and in terms of the mechanical characteristics (in particular, a mechanical strength) and a hygroscopicity, the resin material containing a polyimide resin is preferable. A polyimide resin and an epoxy resin may be mixed to be used. A polyimide resin and/or an epoxy resin may be mixed with a thermoplastic resin and/or an elastomer. Furthermore, a rubber-modified polyimide resin and/or an epoxy resin may be mixed. A thermoplastic resin or an elastomer can be mixed to improve flexibility or toughness. Even when the rubber-modified resin is used, the same effect can be obtained.

A cross-linking reaction and/or a polymerization reaction of the light curing type material is caused by ultraviolet light or visible light, and the light curing type material cures. The light curing type includes a radical polymerization type and a cationic polymerization type, for example. Representative examples of the radical polymerization type material include a combination of an acrylic resin (epoxy modified acrylic resin, urethane modified acrylic resin, and silicone modified acrylic resin) and a photopolymerization initiator. Examples of an ultraviolet radical polymerization initiator include an acetophenone type initiator and a benzophenone type initiator. Examples of a visible light radical polymerization initiator include a benzylic type initiator and a thioxanthone type initiator. A combination of an epoxy compound and a photo cationic polymerization initiator is a representative example of the cationic polymerization type. Examples of a photo cationic polymerization initiator include an iodonium salt-based compound. A resin material having both light curing and thermal curing characteristics can be used also.

The liquid crystal panel 100Pb illustrated in FIG. 16B is different from the liquid crystal panel 100Pa in that the liquid crystal panel 100Pb further includes an adhesive layer 67 between the resistive film 68 and the dielectric substrate 1. Moreover, the liquid crystal panel 100Pb is different from the liquid crystal panel 100Pa in that the protection layer 69 b is formed using a polymer film or glass plate fabricated in advance.

For example, the liquid crystal panel 100Pb including the protection layer 69 b formed of a polymer film is manufactured as below.

First, an insulating polymer film that will become the protection layer 69 b is prepared. Examples of a polymer film include a polyester film made of polyethylene terephthalate, polyethylene naphthalate or the like, and a film made of super engineering plastics such as polyphenylene sulfone, polyimide, or polyamide. A thickness of the polymer film (that is, a thickness of the protection layer 69 b) is greater than or equal to 5 μm and less than or equal to 200 μm, for example.

The resistive film 68 is formed on one surface of this polymer film. The resistive film 68 can be formed by the above method. The resistive film 68 may be patterned, and the polymer film may be also patterned as needed.

The polymer film on which the resistive film 68 is formed (that is, a member integrally formed of the protection layer 69 b and the resistive film 68) is bonded to the dielectric substrate 1 with an adhesive. Examples of the adhesive include the same curable resin as the curable resin used to form the protection layer 69 a described above. Furthermore, a hot-melt type resin material (adhesive) can be used. The hot-melt type resin material contains a thermoplastic resin as a main component, and melts by heating and solidifies by cooling. Examples of the hot-melt type resin material include polyolefin-based (e.g., polyethylene, polypropylene), polyamide-based, and ethylene vinyl acetate-based resins. A reactive urethane-based hot-melt resin material (adhesive) is also available. In terms of adhesive and durability, the reactive urethane-based resin is preferable.

The adhesive layer 67 may be patterned similar to the resistive film 68 and the protection layer (polymer film) 69 b. However, the adhesive layer 67 needs to only fix the resistive film 68 and the protection layer 69 b to the dielectric substrate 1, and may be smaller than the resistive film 68 and the protection layer 69 b.

In place of the polymer film, the glass plate may be also used to form the protection layer 69 b. A manufacturing process may be the same as the case using the polymer film. A thickness of the glass plate is preferably less than or equal to 1 mm and further preferably less than or equal to 0.7 mm. A lower limit of the thickness of the glass plate is not specifically specified, but in terms of handling, the thickness of the glass plate is preferably greater than or equal to 0.3 mm.

In the liquid crystal panel 100Pb illustrated in FIG. 16B, the resistive film 68 formed on the protection layer (polymer film or glass plate) 69 b is fixed to the dielectric substrate 1 via the adhesive layer 67, but the resistive film 68 needs only to be disposed in contact with the dielectric substrate 1, and the resistive film 68 and the protection layer 69 b are not necessarily fixed (bonded) to the dielectric substrate 1. In other words, the adhesive layer 67 may be omitted. For example, the polymer film on which the resistive film 68 is formed (that is, a member integrally formed of the protection layer 69 b and the resistive film 68) may be disposed such that the resistive film 68 is brought into contact with the dielectric substrate 1 and is pressed against the dielectric substrate 1 with the case housing the scanning antenna. For example, since the thermal contact resistance possibly increases when the polymer film on which the resistive film 68 is formed is merely disposed only, the polymer film is preferably pressed against the dielectric substrate to decrease the thermal contact resistance. Using such a configuration allows the member integrally formed of the resistive film 68 and the protection layer (polymer film or glass plate) 69 b to be detachable.

Note that in a case where the resistive film 68 (and the protection layer 69 b) is patterned as described later, the resistive film 68 (and the protection layer 69 b) is preferably fixed to the dielectric substrate 1 to a degree not to shift in a position with respect to the TFT substrate so that the antenna performance does not decrease.

The heater resistive film 68 may be provided anywhere as long as it does not affect the operation of the scanning antenna, but to efficiently heat the liquid crystal material, the resistive film is preferably provided near the liquid crystal layer. Therefore, the heater resistive film 68 is preferably provided on the outer side of the TFT substrate 101 as illustrated in FIGS. 16A and 16B. In addition, the resistive film 68 directly provided on the outer side of the dielectric substrate 1 of the TFT substrate 101 as illustrated in FIG. 16A is preferable, because an energy efficiency is higher, and the controllability of the temperature is higher than those in a case in which the resistive film 68 is provided on the outer side of the dielectric substrate 1 with the adhesive layer 67 therebetween as illustrated in FIG. 16B.

For example, the resistive film 68 may be formed on almost the entire surface of the dielectric substrate 1 of the TFT substrate 104 illustrated in FIG. 13A. The resistive film 68 preferably includes the openings 68 a, 68 b, and 68 c as described for the internal heater structure.

The protection layers 69 a and 69 b may be formed on the entire surface to cover the resistive film 68. As described above, in a case where the protection layer 69 a or 69 b has an adverse effect on antenna characteristics, openings corresponding to the openings 68 a, 68 b, and 68 c of the resistive film 68 may be provided. In this case, the openings of the protection layer 69 a or 69 b are formed inside the openings 68 a, 68 b, and 68 c of the resistive film 68.

To further reduce the influence of the electric field from the heater resistive film 68, a shield conductive layer may be formed. The shield conductive layer is formed on the side of the resistive film 68 closer to the dielectric substrate 1 with an insulating film therebetween, for example. The shield conductive layer is formed on almost the entire surface of the dielectric substrate 1. While the shield conductive layer does not need to include the openings 68 a and 68 b like in the resistive film 68, the opening 68 c is preferably provided therein. The shield conductive layer is formed of, for example, an aluminum layer, and is set to a ground potential. In addition, the resistive film preferably has a distribution of the resistance value so that the liquid crystal layer can be uniformly heated. These structures are similar to the structures of the internal heater structure described above.

The resistive film needs only to heat the liquid crystal layer LC in the transmission and/or reception region R1, and may be provided on an area corresponding to the transmission and/or reception region R1 as an example described above. However, the structure of the resistive film is not limited to this structure. For example, as illustrated in FIG. 2A, in a case where the TFT substrate 101 has an outline capable of defining a rectangular area encompassing the transmission and/or reception region R1, the resistive film may be provided on an area corresponding to the rectangular area encompassing the transmission and/or reception region R1. Of course, the outline of the resistive film is not limited to a rectangle and may be any shape encompassing the transmission and/or reception region R1.

In the above example, the resistive film is disposed on the outer side of the TFT substrate 101, but the resistive film may be disposed on an outer side of the slot substrate 201 (opposite to the liquid crystal layer LC). In this case also, the resistive film may be formed directly on the dielectric substrate 51 similar to the liquid crystal panel 100Pa in FIG. 16A, or the resistive film formed on the protection layer (polymer film or glass plate) with the adhesive layer therebetween may be fixed to the dielectric substrate 51 similar to the liquid crystal panel 100Pb in FIG. 16B. Alternatively, the protection layer on which the resistive film is formed without the adhesive layer (that is, the member integrally formed of the protection layer and the resistive film) may be disposed such that the resistive film is in contact with the dielectric substrate 51. For example, since the thermal contact resistance possibly increases in a case where the polymer film on which the resistive film is formed is merely disposed only, the polymer film is preferably pressed against the dielectric substrate 51 to decrease the thermal contact resistance. Using such a configuration allows the member integrally formed of the resistive film and the protection layer (polymer film or glass plate) to be detachable. Note that in a case where the resistive film (and the protection layer) is patterned, the resistive film (and the protection layer) is preferably fixed to the dielectric substrate to a degree not to shift in a position with respect to the slot substrate so that the antenna performance does not decrease.

In a case where the resistive film is disposed on the outer side of the slot substrate 201, openings are preferably provided in the resistive film at positions corresponding to the slots 57. The resistive film has preferably a thickness enough to transmit microwaves.

Here, the example in which the resistive film is used as the heater section is described, but other than the example, a nichrome line (e.g., winding wire), an infrared light heater section, and the like may be used as the heater section, for example. In the cases like these also, the heater section is preferably disposed not to decrease the antenna performance.

Such an external heater structure may automatically operate, for example, when it is detected that the temperature of the scanning antenna has fallen below a preset temperature. Of course, it may also operate in response to the user operation.

As a temperature control device for making the external heater structure automatically operate, for example, various known thermostats can be used. For example, a thermostat using bimetal may be connected between one of two terminals connected with the resistive film and a power source. Of course, a temperature control device may be used which supplies current to the external heater structure from the power source to prevent the temperature from falling below a preset temperature by the use of a temperature sensor.

Driving Method

Since an antenna unit array of the scanning antenna according to the embodiments of the disclosure has a structure similar to that of an LCD panel, line sequential driving is performed in the same manner as an LCD panel. However, in a case where existing driving methods for LCD panels are applied, the following problems may occur. Problems that may occur in the scanning antenna will be described with reference to the equivalent circuit diagram of one antenna unit of the scanning antenna illustrated in FIG. 17.

First, as mentioned above, since the specific resistance of liquid crystal materials having large dielectric anisotropies Δε_(M) (birefringence Δn with respect to visible light) in the microwave range is low, in a case where driving methods for LCD panels are applied as is, the voltage applied to the liquid crystal layer cannot be sufficiently maintained. Then, the effective voltage applied to the liquid crystal layer decreases, and the electrostatic capacitance value of the liquid crystal capacitance does not reach the target value.

In this way, when the voltage applied to the liquid crystal layer deviates from the predetermined value, the direction in which the gain of the antenna becomes maximum deviates from the intended direction. Then, for example, communication satellites cannot be accurately tracked. To prevent this, an auxiliary capacitance CS is provided electrically in parallel with the liquid crystal capacitance Clc. and the capacitance value C-Ccs of the auxiliary capacitance CS is sufficiently increased. The capacitance value C-Ccs of the auxiliary capacitance CS is preferably set appropriately such that the voltage holding ratio of the liquid crystal capacitance Clc is greater than or equal to 30%, and preferably greater than or equal to 55%. The capacitance value C-Ccs of the auxiliary capacitance CS depends on the area of electrodes CSE1 and CSE2, and the thickness and the dielectric constant of the dielectric layer between the electrode CSE1 and the electrode CSE2. Typically, the same voltage as that of the patch electrode 15 is supplied to the electrode CSE1, and the same voltage as that of the slot electrode 55 is supplied to the electrode CSE2.

In addition, when a liquid crystal material having a low specific resistance is utilized, a voltage drop due to the interface polarization and/or the orientation polarization also occurs. To prevent the voltage drop due to these polarizations, it is conceivable to apply a sufficiently high voltage in anticipation of the voltage drop. However, when a high voltage is applied to a liquid crystal layer having a low specific resistance, a dynamic scattering effect (DS effect) may occur. The DS effect is caused by the convection of ionic impurities in the liquid crystal layer, and the dielectric constant ε_(M) of the liquid crystal layer approaches the average value ((ε_(M)//+2ε_(M)⊥)/3). Also, to control the dielectric constant ε_(M) of the liquid crystal layer in multiple stages (multiple gray scales), it is not always possible to apply a sufficiently high voltage.

To suppress the above-described DS effect and/or the voltage drop due to the polarization, the polarity inversion period of the voltage applied to the liquid crystal layer may be sufficiently shortened. As is well known, in a case where the polarity inversion period of the applied voltage is shortened, a threshold voltage at which the DS effect occurs becomes higher. Accordingly, the polarity inversion frequency may be determined such that the maximum value of the voltage (absolute value) applied to the liquid crystal layer is less than the threshold voltage at which the DS effect occurs. For a polarity inversion frequency of 300 Hz or greater, even in a case where a voltage with an absolute value of 10 V is applied to a liquid crystal layer having a specific resistance of 1×10¹⁰Ω·cm and a dielectric anisotropy Δε (@1 kHz) of about −0.6, a good quality operation can be ensured. In addition, in a case where the polarity inversion frequency (typically equal to twice the frame frequency) is 300 Hz or greater, the voltage drop caused by the polarization is also suppressed. From the viewpoint of power consumption and the like, the upper limit of the polarity inversion period is preferably about less than or equal to 5 KHz.

The polarity inversion frequency of the voltage applied to the liquid crystal layer naturally depends on the liquid crystal material (particularly the specific resistance). Accordingly, depending on the liquid crystal material, even in a case where a voltage with a polarity inversion period of less than 300 Hz is applied, the above described problem does not arise. However, since the liquid crystal material used for the scanning antenna according to the embodiments of the disclosure has a lower specific resistance than that of the liquid crystal material used for LCDs, it is preferable for the liquid crystal layer to be driven at roughly 60 Hz or greater.

As described above, since the viscosity of the liquid crystal material depends on the temperature, it is preferable that the temperature of the liquid crystal layer be appropriately controlled. The physical properties and driving conditions of the liquid crystal material described here are those under the operating temperature of the liquid crystal layer. Conversely, the temperature of the liquid crystal layer is preferably controlled such that it can be driven under the above conditions.

An example of a waveform of a signal used for driving the scanning antenna will be described with reference to FIG. 18A to FIG. 18G. Note that FIG. 18D illustrates the waveform of the display signal Vs (LCD) supplied to the source bus line of the LCD panel for comparison.

FIG. 18A illustrates the waveform of a scanning signal Vg supplied to a gate bus line G-L1, FIG. 18B illustrates the waveform of a scanning signal Vg supplied to a gate bus line G-L2, FIG. 18C illustrates the waveform of a scanning signal Vg supplied to a gate bus line G-L3, FIG. 18E illustrates the waveform of a data signal Vda supplied to the source bus line, FIG. 18F illustrates the waveform of a slot voltage Vidc supplied to the slot electrode of the slot substrate (slot electrode), and FIG. 18G illustrates the waveform of the voltage applied to the liquid crystal layer of each antenna unit.

As illustrated in FIG. 18A to FIG. 18C, the voltage of the scanning signal Vg supplied to the gate bus line sequentially changes from a low level (VgL) to a high level (VgH). VgL and VgH can be appropriately set according to the characteristics of the TFT. For example, VgL=from −5 V to 0 V, and VgH=+20 V. Also, VgL=−20 V and VgH=+20 V are possible. A period from the time when the voltage of the scanning signal Vg of a particular gate bus line switches from the low level (VgL) to the high level (VgH) until the time when the voltage of the next gate bus line switches from VgL to VgH will be referred to as one horizontal scan period (1H). In addition, the period during which the voltage of each gate bus line is at the high level (VgH) will be referred to as a selection period PS. In this selection period PS, the TFTs connected to the respective gate bus lines are turned on, and the current voltage of the data signal Vda supplied to the source bus line is supplied to the corresponding patch electrode. The data signal Vda is, for example, from −15 V to 15 V (an absolute value is 15 V), and, for example, a data signal Vda having different absolute values corresponding to 12 gray scales, or preferably corresponding to 16 gray scales is used.

Here, a case is exemplified where an intermediate voltage is applied to all antenna units. That is, it is assumed that the voltage of the data signal Vda is constant with respect to all antenna units (assumed to be connected to m gate bus lines). This corresponds to the case where the gray levels are displayed on the LCD panel over the whole surface thereof. At this time, dot inversion driving is performed in the LCD panel. That is, in each frame, the display signal voltage is supplied such that the polarities of adjacent pixels (dots) are opposite to each other.

FIG. 18D illustrates the waveform of the display signal of the LCD panel on which the dot inversion driving is performed. As illustrated in FIG. 18D, the polarity of Vs (LCD) is inverted every 1H. The polarity of the Vs (LCD) supplied to a source bus line adjacent to a source bus line supplied with the Vs (LCD) having this waveform is opposite to the polarity of the Vs (LCD) illustrated in FIG. 18D. Furthermore, the polarity of the display signal supplied to all the pixels is inverted for each frame. In the LCD panels, it is difficult to perfectly match the magnitude of the effective voltage applied to the liquid crystal layer between the positive polarity and the negative polarity, and further, the difference in effective voltage becomes a difference in luminance, which is observed as flicker. To make this flicker less noticeable, the pixels (dots) to which voltages of different polarities are applied are spatially dispersed in each frame. Typically, by performing the dot inversion driving, the pixels (dots) having different polarities are arranged in a checkered pattern.

In contrast, in the scanning antenna, the flicker itself is not problematic. That is, it is sufficient for the electrostatic capacitance value of the liquid crystal capacitance to be an intended value, and the spatial distribution of the polarity in each frame is not problematic. Accordingly, from the perspective of low power consumption or the like, it is preferable to reduce the number of times of polarity inversion of the data signal Vda supplied from the source bus line; that is, to lengthen the period of polarity inversion. For example, as illustrated in FIG. 18E, the period of polarity inversion may be set to 10 H (such that polarity inversion occurs every 5 H). Of course, in a case where the number of antenna units connected to each source bus line (typically equal to the number of gate bus lines) is m, the period of polarity inversion of the data signal Vda may be 2 m·H (polarity inversion occurs each m·H). The period of polarity inversion of the data signal Vda may be equal to 2 frames (a polarity inversion occurs each frame).

In addition, the polarity of the data signal Vda supplied from all the source bus lines may be the same. Accordingly, for example, in a particular frame, a positive polarity data signal Vda may be supplied from all the source bus lines, and in the next frame, a negative polarity data signal Vda may be supplied from all the source bus lines.

Alternatively, the polarities of the data signals Vda supplied from the adjacent source bus lines may be opposite to each other. For example, in a particular frame, a positive polarity data signal Vda is supplied from odd-numbered source bus lines, and a negative polarity data signal Vda may be supplied from even-numbered source bus lines. Then, in the next frame, the negative polarity data signal Vda is supplied from the odd-numbered source bus lines, and the positive polarity data signal Vda is supplied from the even-numbered source bus lines. In the LCD panels, such a driving method is referred to as source line inversion driving. In a case where the data signals Vda supplied from adjacent source bus line are made to have opposite polarity, by connecting (short-circuiting) adjacent source bus lines to each other before inverting the polarity of the data signals Vda supplied between frames, it is possible to cancel electric charges stored in the liquid crystal capacitance between adjacent columns. Accordingly, an advantage can be obtained such that the amount of electric charge supplied from the source bus line in each frame can be reduced.

As illustrated in FIG. 18F, the voltage Vidc of the slot electrode is, for example, a DC voltage, and is typically a ground potential. Since the capacitance value of the capacitance (liquid crystal capacitance and auxiliary capacitance) of the antenna units is greater than the capacitance value of the pixel capacitance of the LCD panel (for example, about 30 times in comparison with 20-inch LCD panels), there is no affect from the pull-in voltage due to the parasitic capacitance of the TFT, and even in a case where the voltage Vidc of the slot electrode is the ground potential and the data signal Vda is a positive or negative symmetrical voltage with reference to the ground potential, the voltage supplied to the patch electrode is positive and negative symmetrical voltages. In the LCD panels, although the positive and negative symmetrical voltages are applied to the pixel electrode by adjusting the voltage (common voltage) of the counter electrode in consideration of the pull-in voltage of the TFT, this is not necessary for the slot voltage of the scanning antenna, and the ground potential may be used. Also, although not illustrated in FIG. 18A to FIG. 18G, the same voltage as the slot voltage Vidc is supplied to the CS bus line.

Since the voltage applied to the liquid crystal capacitance of each antenna unit is the voltage of the patch electrode with respect to the voltage Vidc (FIG. 18F) of the slot electrode (that is, the voltage of the data signal Vda illustrated in FIG. 18E), when the slot voltage Vidc is the ground potential, as illustrated in FIG. 18G, the voltage coincides with the waveform of the data signal Vda illustrated in FIG. 18E.

The waveform of the signal used for driving the scanning antenna is not limited to the above example. For example, as described below with reference to FIG. 19A to FIG. 19E and FIG. 20A to FIG. 20E, a Viac having an oscillation waveform may also be used as the voltage of the slot electrode.

For example, signals such as those exemplified in FIG. 19A to FIG. 19E can be used. In FIG. 19A to FIG. 19E, although the waveform of the scanning signal Vg supplied to the gate bus line is omitted, the scanning signal Vg described with reference to FIG. 18A to FIG. 18C is also used here.

As illustrated in FIG. 19A, similar to that illustrated in FIG. 18E, a case where the waveform of the data signal Vda is inverted in polarity at a 10H period (every 5 H) will be exemplified. Here, a case where the amplitude is the maximum value |Vda_(max)| is illustrated as the data signal Vda. As described above, the waveform of the data signal Vda may be inverted in polarity at a two frame period (each frame).

Here, as illustrated in FIG. 19C, the voltage Viac of the slot electrode is an oscillation voltage such that the polarity of the voltage Viac of the slot electrode is opposite to the polarity of the data signal Vda (ON), and the oscillation period of the slot electrode is the same as that of the data signal Vda (ON). The amplitude of the voltage Viac of the slot electrode is equal to the maximum value |Vda_(max)| of the amplitude of the data signal Vda. That is, the slot voltage Viac is set to a voltage that oscillates between −Vda_(max) and +Vda_(max) with the same period of polarity inversion as that of the data signal Vda (ON) and opposite polarity (the phase differs by 180°).

Since the voltage Vlc applied to the liquid crystal capacitance of each antenna unit is the voltage of the patch electrode with respect to the voltage Viac (FIG. 19C) of the slot electrode (that is, the voltage of the data signal Vda (ON) illustrated in FIG. 19A), when the data signal Vda oscillates with the amplitude of ±Vda_(max), the voltage applied to the liquid crystal capacitance has a waveform that oscillates with an amplitude twice Vda_(max) as illustrated in FIG. 19D. Accordingly, the maximum amplitude of the data signal Vda required to make the maximum amplitude of the voltage Vlc applied to the liquid crystal capacitance to be ±Vda_(max) is ±Vda_(max)/2.

Since the maximum amplitude of the data signal Vda can be halved by using such a slot voltage Viac, there is the advantage that a general-purpose driver IC with a breakdown voltage of 20 V or less can be used as a driver circuit for outputting the data signal Vda, for example.

Note that, as illustrated in FIG. 19E, to make the voltage Vlc (OFF) applied to the liquid crystal capacitance of each antenna unit zero, as illustrated in FIG. 19B, it may be preferable for the data signal Vda (OFF) to have the same waveform as that of the slot voltage Viac.

Consider, for example, a case where the maximum amplitude of the voltage Vlc applied to the liquid crystal capacitance is ±15 V. When the Vidc illustrated in FIG. 18F is used as the slot voltage and Vidc=0 V, the maximum amplitude of Vda illustrated in FIG. 18E becomes ±15 V. In contrast, when the Viac illustrated in FIG. 19C is used as the slot voltage and the maximum amplitude of Viac is ±7.5 V, the maximum amplitude of Vda (ON) illustrated in FIG. 19A becomes ±7.5 V.

When the voltage Vlc applied to the liquid crystal capacitance is 0 V, the Vda illustrated in FIG. 18E may be set to 0 V, and the maximum amplitude of the Vda (OFF) illustrated in FIG. 19B may be set to ±7.5 V.

In a case where the Viac illustrated in FIG. 19C is utilized, the amplitude of the voltage Vlc applied to the liquid crystal capacitance is different from the amplitude of Vda, and therefore appropriate conversions are necessary.

Signals such as those exemplified in FIG. 20A to FIG. 20E can also be used. The signals illustrated in FIG. 20A to FIG. 20E are the same as the signals illustrated in FIG. 19A to FIG. 19E in that the voltage Viac of the slot electrode is an oscillation voltage such that the oscillation phase thereof is shifted by 180° from the oscillation phase of the data signal Vda (ON) as illustrated in FIG. 20C. However, as illustrated in each of FIG. 20A to FIG. 20C, all of the data signals Vda (ON), Vda (OFF), and the slot voltage Viac are voltages oscillating between 0 V and a positive voltage. The amplitude of the voltage Viac of the slot electrode is equal to the maximum value |Vda_(max)| of the amplitude of the data signal Vda.

When such a signal is utilized, the driving circuit only needs to output a positive voltage, which contributes to cost reduction. As described above, even in a case where a voltage oscillating between 0 V and a positive voltage is used, as illustrated in FIG. 20D, the polarity of the voltage Vlc (ON) applied to the liquid crystal capacitance is inverted. In the voltage waveform illustrated in FIG. 20D, + (positive) indicates that the voltage of the patch electrode is higher than the slot voltage, and − (negative) indicates that the voltage of the patch electrode is lower than the slot voltage. That is, the direction (polarity) of the electric field applied to the liquid crystal layer is inverted similarly to the other examples. The amplitude of the voltage Vlc (ON) applied to the liquid crystal capacitance is Vda_(max).

Note that, as illustrated in FIG. 20E, to make the voltage Vlc (OFF) applied to the liquid crystal capacitance of each antenna unit zero, as illustrated in FIG. 20B, it may be preferable for the data signal Vda (OFF) to have the same waveform as that of the slot voltage Viac.

The driving method described with reference to FIG. 19A to FIG. 19E and FIG. 20A to FIG. 20E of oscillating (inverting) the voltage Viac of the slot electrodes corresponds to a driving method of inverting the counter voltage in the driving method of the LCD panels (sometimes referred to as a “common inversion drive”). In the LCD panels, since the flicker cannot be sufficiently suppressed, the common inversion drive is not utilized. In contrast, in the scanning antennas, since the flicker does not matter, the slot voltage can be inverted. Oscillation (inversion) is performed in each frame, for example (the 5H in FIG. 19A to FIG. 19E and FIG. 20A to FIG. 20E is set to 1 V (vertical scanning period or frame)).

In the above description, although an example of the voltage Viac of the slot electrode is described in which one voltage is applied; that is, an example in which a common slot electrode is provided for all patch electrodes, the slot electrode may be divided corresponding to one row or two or more rows of the patch electrode. Here, a row refers to a set of patch electrodes connected to one gate bus line with a TFT therebetween. By dividing the slot electrode into a plurality of row portions in this way, the polarities of the voltages of the respective portions of the slot electrode can be made independent from each other. For example, in a freely-selected frame, the polarity of the voltage applied to the patch electrodes can be inverted between the patch electrodes connected to adjacent gate bus lines. In this way, it is possible to perform row inversion in which the polarity is inverted not only for each single row (1H inversion) of the patch electrode, but also m row inversion (mH inversion) in which the polarity is inverted for every two or more rows. Of course, row inversion and frame inversion can be combined.

From the viewpoint of simplicity of driving, it is preferable that the polarity of the voltage applied to the patch electrode be the same in any frame, and the polarity be inverted every frame.

Example of Antenna Unit Array and Connection of Gate Bus Line and Source Bus Line

In the scanning antenna according to the embodiments of the disclosure, the antenna units are arranged concentrically, for example.

For example, in a case where the antenna units are arranged in m concentric circles, one gate bus line is provided for each circle, for example, such that a total of m gate bus lines is provided. For example, assuming that the outer diameter of the transmission and/or reception region R1 is 800 mm, m is 200, for example. Assuming that the innermost gate bus line is the first one, n (30, for example) antenna units are connected to the first gate bus line, and nx (620, for example) antenna units are connected to the mth gate bus line.

In such an arrangement, the number of antenna units connected to each gate bus line is different. In addition, although m antenna units are connected to a number n of the source bus lines that are also connected to the antenna units constituting the innermost circle, among the nx number of source bus lines connected to nx number antenna units that constitute the outermost circle, the number of antenna units connected to other source bus lines is less than m.

In this way, the arrangement of antenna units in the scanning antenna is different from the arrangement of pixels (dots) in the LCD panel, and the number of connected antenna units differs depending on the gate bus line and/or source bus line. Accordingly, in a case where the capacitances (liquid crystal capacitances÷auxiliary capacitances) of all the antenna units are set to be the same, depending on the gate bus line and/or the source bus line, the electrical loads of the antenna units connected thereto differ. In such a case, there is a problem where variations occur in the writing of the voltage to the antenna unit.

Accordingly, to prevent this, the capacitance value of the auxiliary capacitance is preferably adjusted, or the number of antenna units connected to the gate bus line and/or the source bus line is preferably adjusted, for example, to make the electrical loads of the antenna units connected to the gate bus lines and the source bus lines substantially the same.

Monitoring Voltage Holding Ratio of Liquid Crystal Capacitance

As described above, the scanning antenna according to the embodiments of the disclosure uses a nematic liquid crystal material having a large dielectric anisotropy Δε_(M) (birefringence index Δn for visible light) for microwaves. Examples of liquid crystal materials having a large dielectric anisotropy Δε_(M) in the microwave range include an isothiocyanate group (—NCS) or a thiocyanate group (—SCN). For example, any atomic group represented by the following chemical formula (Formula 1) is included.

Since the specific resistance of a liquid crystal material including the isothiocyanate group or the thiocyanate group is low, the retention ratio of the voltage applied to the liquid crystal capacitance is low. When the liquid crystal material deteriorates, the specific resistance further decreases, and the voltage holding ratio (sometimes abbreviated as “VHR”) further decreases.

Liquid crystal materials including an isothiocyanate group or a thiocyanate group have a strong polarity, and their chemical stability is lower than that of the liquid crystal materials presently used for LCDs. Since the isothiocyanate group and the thiocyanate group have strong polarity, they easily absorb moisture, and may react with metal ions (for example, Cu ions when the slot electrode includes a Cu layer). In addition, when a DC voltage is continuously applied, an electrical decomposition reaction may occur. Also, liquid crystal materials including an isothiocyanate group or a thiocyanate group absorb light from the ultraviolet region to approximately 430 nm, and are easily photo-decomposed. In addition, liquid crystal materials including an isothiocyanate group or a thiocyanate group are also relatively weak to heat. Due to these factors, the specific resistance of the liquid crystal material decreases, and/or the ionic impurities increase, and thus, the VHR of the liquid crystal capacitance decreases. When the VHR of the liquid crystal capacitance of each antenna unit decreases, the characteristics of the scanning antenna deteriorate.

A relationship between a reduction in the VHR and the antenna characteristics will be described with reference to FIG. 21A and FIG. 21B. FIG. 21A and FIG. 21B are schematic graphs in which the horizontal axis represents the voltage applied to the liquid crystal capacitance, and the vertical axis represents the resonance frequency that serves as the antenna characteristic.

As illustrated in FIG. 21A, when the voltage holding ratio of the liquid crystal capacitance decreases, the effective voltage applied to the liquid crystal layer decreases, and the target voltage is not applied to the liquid crystal layer. As a result, the phase difference provided to the microwaves by the liquid crystal layer of each antenna unit is shifted from a predetermined value. When the phase difference shifts from the predetermined value, the antenna characteristics deteriorate. This deterioration of the antenna characteristics can be evaluated as a shift in the resonance frequency, for example. In reality, since the scanning antenna is designed to maximize the gain at a predetermined resonance frequency, the decrease in the VHR appears as a decrease in the gain, for example.

As illustrated in FIG. 21A, when the VHR of the liquid crystal capacitance decreases from 100% to 15%, the resonance frequency increases when the same voltage is applied. As illustrated in FIG. 21B, in a case in which a phase difference of 4 gray scales (0 gray scale level, 1 gray scale level, 2 gray scale level, and 3 gray scale level) is applied to a microwave, when a voltage set when the VHR is 100% is applied, naturally, the predetermined phase difference cannot be provided. As illustrated in FIG. 21B, this appears as a shift in the resonance frequency, resulting in a decrease in the gain. In the scanning antenna according to the embodiments of the disclosure, the reduction in the VHR is monitored, and the voltage is adjusted so as to obtain a predetermined gray scale on the basis of the value of the VHR, such that a predetermined phase difference can be provided even in a case where the VHR decreases.

The embodiments of the disclosure are not limited to scanning antennas, and can be widely applied to liquid crystal devices including the LCD panels. The liquid crystal layer of the antenna unit of the scanning antenna provides a predetermined phase difference to microwaves, whereas the liquid crystal layer of the pixels of an LCD provides a predetermined phase difference to visible light (polarized light). For example, in a normally black mode LCD, when the VHR of the liquid crystal capacitance of a pixel decreases, the transmittance decreases, and a predetermined gray scale cannot be displayed. According to the embodiments of the disclosure, the VHR is monitored and the voltage (source voltage) is adjusted on the basis of the value of the VHR, such that a predetermined gray scale display can be performed even in a case where the VHR decreases.

Note that, generally, since the liquid crystal materials used in the LCD panels do not include an isothiocyanate group or a thiocyanate group, the cause of deterioration of the liquid crystal material as described above is unlikely to arise. Accordingly, in normal LCD panels, there is a tendency that it is unlikely for problems to arise in which the voltage applied to the liquid crystal layer shifts from the target value due to the decrease in the voltage holding ratio of the liquid crystal capacitance. However, by applying the embodiments of the disclosure to the LCD panels, it is possible to further suppress the occurrence of such problems.

The evaluation of the voltage holding ratio is generally performed as an evaluation item of TFT type LCD panels. For example, WO 2008/090786 discloses a method for electrically measuring the voltage holding ratio of the liquid crystal capacitance of a pixel of an LCD panel. For reference, with regard to the method of measuring the voltage holding ratio of the liquid crystal capacitance, in particular, the entire content of WO 2008/090786 is incorporated herein. Note that in the measurement method disclosed in this publication, the voltage holding ratio cannot be measured when the LCD panel is in a display state.

The embodiments of the disclosure can be widely applied not only to scanning antennas, but also to liquid crystal devices having a configuration for applying a voltage to a liquid crystal capacitance, such as the LCD panels. However, as described above, since the scanning antenna uses a liquid crystal material having a relatively low specific resistance, the effect achieved by the embodiments of the disclosure is significant.

In the following, an example of the scanning antenna according to the embodiments will be described.

The structure of a scanning antenna 1000A will be described with reference to FIG. 22 to FIG. 25C. FIG. 22 is a schematic plan view illustrating the scanning antenna 1000A.

As illustrated in FIG. 22, the scanning antenna 1000A includes a VHR monitoring capacitance section MV and a VHR monitoring circuit MD in the non-transmission and/or reception region R2. The VHR monitoring capacitance section MV includes a VHR monitoring capacitance C_(MV) having the same configuration as that of the liquid crystal capacitance Clc of the antenna unit. That is, the pair of electrodes included in the VHR monitoring capacitance C_(MV) are preferably formed of the same material as that of the pair of electrodes of the liquid crystal capacitance Clc, and are more preferably formed from the same conductive film. The liquid crystal layer LC of the VHR monitoring capacitance C_(MV) is a single liquid crystal layer that is connected to the liquid crystal layer LC of the transmission and/or reception region R1, and the thickness of the liquid crystal layer LC is controlled to be substantially the same. In addition, the pair of alignment films in contact with the liquid crystal layer LC of the VHR monitoring capacitance C_(MV) are common to the pair of alignment films formed in the transmission and/or reception region R1.

The configuration of the scanning antenna 1000A is similar to the structure of the scanning antenna 1000 described with reference to FIGS. 2A and 2B, for example, with the exception of the VHR monitoring capacitance section MV and the VHR monitoring circuit MD. In the following, a description and/or an illustration of the structure common to the scanning antenna 1000 may be omitted. FIG. 22 illustrates the structure of the scanning antenna 1000A in a simplified manner.

As illustrated in FIG. 23, the scanning antenna 1000A further includes a measurement electrode transfer section M2P, a first measurement electrode terminal section M1T, and a second measurement electrode terminal section M2T in the non-transmission and/or reception region R2.

The structures of the VHR monitoring capacitance section MV, the measurement electrode transfer section M2P, the first measurement electrode terminal section M1T, and the second measurement electrode terminal section M2T will be described with reference to FIG. 23 to FIG. 25C. FIG. 23 is a schematic plan view illustrating the non-transmission and/or reception region R2 of the scanning antenna 1000A. FIG. 24A and FIG. 24B are schematic cross-sectional views illustrating the non-transmission and/or reception region R2 of the scanning antenna 1000A along the lines A-A′ and B-B′ in FIG. 23, respectively. FIG. 25A to FIG. 25C are schematic plan views illustrating regions corresponding to the non-transmission and/or reception region R2 of the scanning antenna 1000A illustrated in FIG. 23, where FIG. 25A and FIG. 25B are schematic plan views of a TFT substrate 100A included in the scanning antenna 1000A, and FIG. 25C is a schematic plan view of a slot substrate 200A included in the scanning antenna 1000A. FIG. 25A is a diagram illustrating the gate metal layer, FIG. 25B is a diagram illustrating the patch metal layer, and FIG. 25C is a diagram illustrating a layer including the slot electrode 55.

Note that, in FIG. 24A and FIG. 24B, the liquid crystal panel of the scanning antenna is illustrated, and an illustration of the dielectric layer (air layer) 54 and the reflective conductive plate 65 in FIG. 1 is omitted.

VHR Monitoring Capacitance Section MV

As illustrated in FIG. 23 to FIG. 24B, the VHR monitoring capacitance section MV includes a VHR monitoring capacitance C_(MV). The VHR monitoring capacitance C_(MV) includes a liquid crystal layer LC and a first measurement electrode ME1 and a second measurement electrode ME2 that are opposed to each other with the liquid crystal layer LC interposed therebetween. Strictly speaking, an alignment film is provided between the first measurement electrode ME1 and the liquid crystal layer LC, and between the second measurement electrode ME2 and the liquid crystal layer LC. The first measurement electrode ME1 and the second measurement electrode ME2 are disposed inside the seal region Rs (closer to the transmission and/or reception region R1 than the seal region Rs).

The scanning antenna 1000A includes the VHR monitoring capacitance section MV. This allows the voltage holding ratio of the VHR monitoring capacitance C_(MV) to be measured.

It is preferable that the location of the VHR monitoring capacitance C_(MV), that is, the locations of the first measurement electrode ME1 and the second measurement electrode ME2, be separated from the seal region Rs by 10 mm or more. That is, it is preferable that the first measurement electrode ME1 and the second measurement electrode ME2 be disposed so as not to overlap a region of less than 10 mm from the seal region Rs. This is to prevent the seal resin that forms the seal region Rs from being affected by ionic impurities (arising from uncured components, for example) eluted from the seal resin into the liquid crystal layer LC.

Since many antenna unit regions are farther from the seal region Rs than the VHR monitoring capacitance section MV, the liquid crystal layer LC of the liquid crystal capacitance Clc of the antenna unit regions in the transmission and/or reception region R1 tends to be less affected by the resin that forms the seal region Rs than the liquid crystal layer LC of the VHR monitoring capacitance C_(MV) of the non-transmission and/or reception region R2 does. When the liquid crystal layer LC of the VHR monitoring capacitance C_(MV) is influenced by the resin that forms the seal region Rs, the voltage holding ratio of the VHR monitoring capacitance C_(MV) greatly differs from the voltage holding ratio of the liquid crystal capacitance Clc in the antenna unit regions. In this case, it may be difficult to estimate the voltage holding ratio of the liquid crystal capacitance Clc in the antenna unit regions from the measured value of the voltage holding ratio of the VHR monitoring capacitance C_(MV). By disposing the first measurement electrode ME1 and the second measurement electrode ME2 at a distance of 10 mm or more from the seal region Rs, the occurrence of such a problem can be suppressed.

As illustrated in FIG. 24A, the VHR monitoring capacitance section MV includes, on the TFT substrate 100A, a first measurement electrode connection section 3 p 1, an insulating layer 13 covering the first measurement electrode connection section 3 p 1, and a first measurement electrode ME1 formed on the insulating layer 13. The first measurement electrode connection section 3 p 1 is formed of the same conductive film as that of the gate electrode 3. The insulating layer 13 includes at least one opening 13 a that reaches the first measurement electrode connection section 3 p 1. The first measurement electrode ME1 is formed of the same conductive film as that of the patch electrode 15. The first measurement electrode ME1 is formed on the insulating layer 13 and in the opening 13 a, and is in contact with the first measurement electrode connection section 3 p 1 within the opening 13 a.

The insulating layer 13 includes, for example, the gate insulating layer 4 and the first insulating layer 11 (see FIG. 3A).

The VHR monitoring capacitance section MV may further include the second insulating layer 17 covering the first measurement electrode ME1.

As illustrated in FIG. 24A, the VHR monitoring capacitance section MV includes, in the slot substrate 200A, a second measurement electrode ME2 including a portion opposed to the first measurement electrode ME1 with the liquid crystal layer LC therebetween. The second measurement electrode ME2 is formed of the same conductive film as that of the slot electrode 55, and is electrically separated from an extending section 55 e of the slot electrode 55. The “extending section 55 e of the slot electrode 55” is a portion extending from the slot electrode 55 to the non-transmission and/or reception region R2. The extending section 55 e of the slot electrode 55 can be omitted.

The VHR monitoring capacitance section MV may further include a fourth insulating layer 58 covering the second measurement electrode ME2.

Each of the first measurement electrode ME1 and the second measurement electrode ME2 has a rectangular shape with approximately 1 cm long sides. Here, the shape and size of the first measurement electrode ME are those when viewed from the normal direction of the TFT substrate 100A, and the shape and size of the second measurement electrode ME2 are those when viewed from the normal direction of the slot substrate 200A. It is sufficient for the shapes and sizes of the first measurement electrode ME1 and the second measurement electrode ME2 to include portions where the first measurement electrode ME1 and the second measurement electrode ME2 oppose each other with the liquid crystal layer LC interposed therebetween and not to be limited to specific shapes and sizes. The first measurement electrode ME1 and the second measurement electrode ME2 may have the same shape and size, or may differ in shape and/or size. To more precisely measure the voltage holding ratio of the VHR monitoring capacitance C_(MV), it is preferable that the first measurement electrode ME1 and the second measurement electrode ME2 have the same shape and size.

The structure of the VHR monitoring capacitance section MV is not limited to what is illustrated. For example, the first measurement electrode connection section 3 p 1 may not be formed using the same conductive film as that of the gate electrode 3. A transfer terminal connection section 15 pt does not need to be formed using the same conductive film as that of the patch electrode 15. It is, however, preferable to form these in any conductive layer of the conductive layers (including the gate metal layer, the source metal layer, and the patch metal layer) of the TFT substrate 100A. In this case, the VHR monitoring capacitance section can be formed without increasing the number of manufacturing steps (for example, the number of photomasks) of the scanning antenna.

The insulating layer 13 may include one opening 13 a or a plurality of openings 13 a. In this example, since the insulating layer 13 includes the plurality of openings 13 a, the stability of the electrical connection between the first measurement electrode ME1 and the first measurement electrode connection section 3 p 1 can be improved. The openings 13 a do not need to be provided in the VHR monitoring capacitance section MV. For example, the insulating layer 13 may include at least one opening in a region other than the VHR monitoring capacitance section MV, an extending section of the first measurement electrode ME1 may be formed on the insulating layer 13 and in the opening, and the extending section of the first measurement electrode ME may be in contact with the first measurement electrode connection section 3 p 1 within the opening.

Measurement Electrode Transfer Section M2P and Measurement Electrode Transfer Terminal Portion M2PT

As illustrated in FIG. 23 to FIG. 24B, the measurement electrode transfer section M2P is a connection section between the measurement electrode transfer terminal section M2PT of the TFT substrate 100A and the second measurement electrode ME2. In this example, the measurement electrode transfer section M2P is disposed in the seal region Rs. For example, similar to the transfer section described with reference to FIG. 7, the measurement electrode transfer terminal section M2P and the second measurement electrode ME2 are connected with a resin (seal resin) 73 (also referred to as “sealing portion 73”) including the conductive beads 71 therebetween. The sealing portion 73 including the conductive beads 71 has conductivity only in the vertical direction of FIG. 24A and FIG. 24B, and does not have conductivity in a direction perpendicular to the plane of the drawings.

In the measurement electrode transfer section M2P, the TFT substrate 100A includes the measurement electrode transfer terminal section M2PT.

The measurement electrode transfer terminal section M2PT includes a second measurement electrode connection section 3 p 2, the insulating layer 13 covering the second measurement electrode connection section 3 p 2, and the transfer terminal connection section 15 pt formed on the insulating layer 13. The second measurement electrode connection section 3 p 2 is formed using the same conductive film as that of the first measurement electrode connection section 3 p 1, and is electrically separated from the first measurement electrode connection section 3 p 1. The insulating layer 13 includes at least one opening 13 b that reaches the second measurement electrode connection section 3 p 2. The transfer terminal connection section 15 pt is formed using the same conductive film as that of the patch electrode 15. The transfer terminal connection section 15 pt is formed on the insulating layer 13 and in the opening 13 b, and is in contact with the second measurement electrode connection section 3 p 2 within the opening 13 b.

It is preferable that the measurement electrode transfer terminal section M2PT includes the same layered structure as that of the transfer terminal section PT (see FIG. 4C, for example), for example.

In the measurement electrode transfer section M2P, the slot substrate 200A includes an extending section ME2 e of the second measurement electrode ME2 and the fourth insulating layer 58 covering the extending section ME2 e of the second measurement electrode ME2, and the fourth insulating layer 58 includes at least one opening 58 a that exposes a part of the extending section ME2 e of the second measurement electrode ME2.

In the measurement electrode transfer section M2P, the second measurement electrode ME2 is electrically connected to the second measurement electrode connection section 3 p 2 of the TFT substrate 100A.

Note that the measurement electrode transfer section M2P (measurement electrode transfer terminal section M2PT) does not need to be disposed within the seal region Rs. For example, the measurement electrode transfer section M2P may be disposed outside the seal region Rs in the non-transmission and/or reception region R2.

The structure of the measurement electrode transfer terminal section M2PT is not limited to what is illustrated. For example, the second measurement electrode connection section 3 p 2 does not need to be formed using the same conductive film as that of the first measurement electrode connection section 3 p 1. The transfer terminal connection section 15 pt does not need to be formed using the same conductive film as that of the patch electrode 15. From the viewpoint of suppressing an increase in the number of manufacturing steps of the scanning antenna (the number of photomasks), these are preferably formed in any conductive layer of the conductive layers (including the gate metal layer, the source metal layer, and the patch metal layer) of the TFT substrate 100A.

As illustrated in FIG. 25B, the patch metal layer may include a seal region section 15 ps electrically isolated from the transfer terminal connection section 15 pt within the seal region Rs. It is preferable that the TFT substrate 100A has the same layered structure (see FIG. 4C, for example) as that of the transfer terminal section PT within the seal region Rs, for example. This allows a transfer section that connects the electrodes or the terminals of the TFT substrate 100A and the electrodes or the terminals of the slot substrate 200A to be formed in the seal region Rs.

First Measurement Electrode Terminal Section M1T and Second Measurement Electrode Terminal Section M2T

As illustrated in FIG. 23 to FIG. 24B, the first measurement electrode terminal section M1T and the second measurement electrode terminal section M2T are provided on the TFT substrate 100A outside the seal region Rs (the side opposite to the liquid crystal layer LC side of the seal region Rs) within the non-transmission and/or reception region R2 of the scanning antenna 1000A. The first measurement electrode terminal section M1T and the second measurement electrode terminal section M2T do not include the liquid crystal layer LC and the slot substrate 200A. That is, the TFT substrate 100A is exposed at the first measurement electrode terminal section M1T and the second measurement electrode terminal section M2T.

As illustrated in FIG. 24A, the first measurement electrode terminal section M1T includes the first measurement electrode connection section 3 p 1; and the insulating layer 13 and the second insulating layer 17 covering the first measurement electrode connection section 3 p 1. The insulating layer 13 and the second insulating layer 17 include a contact hole CH7 that reaches the first measurement electrode connection section 3 p 1.

The contact hole CH7 may be covered with a transparent conductive layer (not illustrated). That is, the first measurement electrode terminal section M1T further includes a transparent conductive layer formed on the second insulating layer 17 and in the contact hole CH7, and the transparent conductive layer may be in contact with the first measurement electrode connection section 3 p 1 within the contact hole CH7.

As illustrated in FIG. 24B, the second measurement electrode terminal section M2T includes the second measurement electrode connection section 3 p 2; and the insulating layer 13 and the second insulating layer 17 covering the second measurement electrode connection section 3 p 2. The insulating layer 13 and the second insulating layer 17 include a contact hole CH8 that reaches the second measurement electrode connection section 3 p 2.

The contact hole CH8 may be covered with a transparent conductive layer (not illustrated). That is, the second measurement electrode terminal section M2T further includes a transparent conductive layer formed on the second insulating layer 17 and in the contact hole CH8, and the transparent conductive layer may be in contact with the second measurement electrode connection section 3 p 2 within the contact hole CH8.

As illustrated in FIG. 25A, in this example, the first measurement electrode connection section 3 p 1 includes a section that overlaps with the first measurement electrode ME1, a section that forms the first measurement electrode transfer section M1T, and a section that straddles the seal region Rs and extends between the two sections. As illustrated in FIG. 25B, the second measurement electrode connection section 3 p 2 includes a section that forms the second measurement electrode terminal section M2T, a section that forms the measurement electrode transfer terminal section M2PT, and a section that extends between the two sections.

VHR Monitoring Circuit MD

The scanning antenna 1000A includes the VHR monitoring circuit MD. The VHR monitoring circuit MD has the configuration illustrated in FIG. 26A and FIG. 26B (with the exception of the VHR monitoring capacitance section MV), for example. The configuration illustrated in FIG. 26A (with the exception of the VHR monitoring capacitance section MV) may be referred to as a pulse voltage supply circuit 93, and the configuration illustrated in FIG. 26B (with the exception of the VHR monitoring capacitance section MV) may be referred to as a voltage monitor circuit 94.

FIG. 26A and FIG. 26B illustrate examples in which the VHR monitoring capacitance section MV includes, in addition to the VHR monitoring capacitance C_(MV), a monitoring auxiliary capacitance CS_(MV) electrically connected in parallel with the VHR monitoring capacitance C_(MV). In the antenna unit, as described above, the auxiliary capacitance CS is provided electrically in parallel with the liquid crystal capacitance Clc (see FIG. 17). The auxiliary capacitance CS acts to improve the VHR of the liquid crystal capacitance Clc. Similar to this, the monitoring auxiliary capacitance CS_(MV) electrically connected in parallel with the VHR monitoring capacitance C_(MV) may also be provided in the VHR monitoring capacitance section MV. In the case that the monitoring auxiliary capacitance CS_(MV) is provided, it is preferable to set the capacitance value C-CS_(MV) such that the ratio (C-CS_(MV)/C-C_(MV)) of the capacitance value C-CS_(MV) of the monitoring auxiliary capacitance CS_(MV) to the capacitance value C-C_(MV) of the VHR monitoring capacitance C_(MV) equals the ratio (C-Ccs/C_(Clc)) of the capacitance value C-Ccs of the auxiliary capacitance CS to the capacitance value C_(Clc) of the liquid crystal capacitance Clc in the antenna unit. In addition, the pair of electrodes CSE1 b and CSE2 b of the monitoring auxiliary capacitance CS_(MV) are preferably formed of the same material as that of the pair of electrodes CSE1 and CSE2 (see FIG. 17) of the auxiliary capacitance CS, and are more preferably formed from the same conductive film. Similarly, it is preferable that the dielectric layer of the monitoring auxiliary capacitance CS_(MV) is also formed of the same material as that of the dielectric layer of the auxiliary capacitance CS, and is more preferably formed from the same dielectric film. In this way, by setting a configuration of the VHR monitoring capacitance C_(MV) to a configuration similar to the liquid crystal capacitance Clc of the antenna unit, it is possible to set the value of the VHR of the VHR monitoring capacitance C_(MV) to a value directly comparable to the VHR value of the liquid crystal capacitance Clc.

However, the monitoring auxiliary capacitance CS_(MV) may be omitted, and in this case, the correlation between the VHR value of the VHR monitoring capacitance C_(MV) and the VHR value of the liquid crystal capacitance Clc may be obtained in advance. In the following description, it is assumed that the monitoring auxiliary capacitance CS_(MV) is omitted for the simplicity of description.

FIG. 26A illustrates a configuration (pulse voltage supply circuit 93) in a case where the VHR monitoring circuit MD supplies a pulse voltage to the VHR monitoring capacitance C_(MV), and FIG. 26B illustrates a configuration (voltage monitoring circuit 94) in a case where the VHR monitoring circuit MD monitors the change in the potential of the first measurement electrode ME1 of the VHR monitoring capacitance C_(MV). The configuration illustrated in FIG. 26A and the configuration illustrated in FIG. 26B can be switched, for example, by providing switches (two switches) and switching the connection relation to the inverting input terminal (−) of the amplifier (an operational amplifier in the illustrated example). Alternatively, the VHR monitoring circuit MD may have the configuration illustrated in FIG. 26A and the configuration illustrated in FIG. 26B as separate circuits. In the VHR monitoring circuit MD, a predetermined pulse voltage is applied to the VHR monitoring capacitance C_(MV) (FIG. 26A), and subsequently, the change in the potential of the first measurement electrode ME1 is monitored (FIG. 26B).

As illustrated in FIG. 26A, the VHR monitoring circuit MD (the pulse voltage supply circuit 93) includes resistors Ra, Rb, and Rc, an operational amplifier (amplifier) 98 p, and a voltage monitor 99. The operational amplifier 98 p amplifies (non-inversion amplification) the pulse voltage input from INPUT with the gain determined by the ratio between the value of the resistance Ra and the value of the resistance Rb, and outputs the amplified voltage to the first measurement electrode ME1 of the VHR monitoring capacitance C_(MV). At this time, the pulse voltage supplied to the first measurement electrode ME1 is set to have the same waveform as that of the gray scale voltage supplied to the liquid crystal capacitance Clc of the antenna unit. For example, the pulse width is 60 μs, the pulse interval is 3.33 ms, and the polarity is inverted for each pulse (in the case of 300 Hz polarity inversion driving).

After the pulse voltage is applied to the first measurement electrode ME1, the VHR monitoring circuit MD monitors the change in the potential of the first measurement electrode ME1 at the voltage monitor 99 using the configuration illustrated in FIG. 26B. As illustrated in FIG. 26B, the VHR monitoring circuit MD (the voltage monitoring circuit 94) includes the resistors Ra, Rb, and Rc, an operational amplifier (amplifier) 98 i, and the voltage monitor 99. In the configuration illustrated in FIG. 26B, the second measurement electrode ME2 of the VHR monitoring capacitance C_(MV) is connected to the inverting input terminal (−) of the operational amplifier 98 i. That is, the VHR monitoring circuit MD includes a feedback circuit that negatively feeds back the output of the operational amplifier 98 i via the VHR monitoring capacitance C_(MV). At this time, the resistance Ra, the resistance Rb and the VHR monitoring capacitance C_(MV) constitute an integrator. Accordingly, in the configuration of FIG. 26B, when the resistance or the capacitance of the VHR monitoring capacitance C_(MV) changes, the output voltage of the operational amplifier 98 i changes. By monitoring the change in the output voltage at the voltage monitor 99 connected to the output of the operational amplifier 98 i with the resistance Rc interposed therebetween, it becomes possible to obtain the voltage holding ratio of the VHR monitoring capacitance C_(MV). For example, a circuit (not illustrated) for receiving the output of the voltage monitor 99 and obtaining the voltage holding ratio of the VHR monitoring capacitance C_(MV) may be further provided. Note that the value of the resistance Rc can be adjusted so as to achieve impedance matching with the voltage monitor 99. The resistance Rc may also serve as a multiplier.

As will be described in detail later, the scanning antenna according to the embodiments of the disclosure determines the gray scale voltage to be supplied to each antenna unit according to the voltage holding ratio of the VHR monitoring capacitance C_(MV). The relationship between the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gray scale voltage to be supplied to each antenna unit is obtained in advance. Note that it is not strictly necessary to configure the VHR monitoring capacitance C_(MV) such that the voltage holding ratio of the VHR monitoring capacitance C_(MV) can be regarded as the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit, and it is sufficient for the scanning antenna to have a fixed relationship between the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit. In addition, it is not strictly necessary to obtain the voltage holding ratio, and, for example, in a case where the relationship between the output voltage (for example, the output voltage at a constant time after the application of the pulse voltage) of the voltage monitor 99 and the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit is obtained in advance, the gray scale voltage to be supplied to each antenna unit can be determined on the basis of this relationship.

In addition, as will be described later, the determination of the gray scale voltage may be performed with a look-up table, by an arithmetic circuit, or by a human (user).

Here, although an example is described in which the gray scale voltage to be supplied to each antenna unit is determined on the basis of the voltage holding ratio (the voltage change) of one VHR monitoring capacitance C_(MV), the determination method is not limited to this. A plurality of VHR monitoring capacitances C_(MV) may be provided on the periphery of the transmission and/or reception region R1 to determine the gray scale voltage to be supplied to each antenna unit on the basis of the average of the voltage holding ratios (the voltage changes) of the VHR monitoring capacitances C_(MV).

In addition, in a case in which the liquid crystal panel (TFT substrate/liquid crystal layer/slot substrate) of one scanning antenna is manufactured by tiling a plurality of sub liquid crystal panels, at least one VHR monitoring capacitance C_(MV) may be provided for each of the sub liquid crystal panels, and the gray scale voltages to be supplied to each individual antenna unit may be determined independently.

Driving Method

A driving circuit 90 included in the scanning antenna 1000A and a driving method of the scanning antenna 1000A will be described with reference to FIG. 27. FIG. 27 is a block diagram schematically illustrating the driving circuit 90 included in the scanning antenna 1000A. The driving circuit 90 includes the above-described VHR monitoring circuit MD.

The driving method of the scanning antenna 1000A includes a step of determining a gray scale voltage to be supplied to each antenna unit on the basis of the voltage holding ratio of the VHR monitoring capacitance C_(MV).

The driving circuit 90 includes a signal converter 91, a control circuit 92, a gate driver GD, a source driver SD, and a timing controller 95.

The signal converter 91 receives an input signal S from an external source, and outputs a signal S′ to the control circuit 92. The control circuit 92 sends a control signal to the gate driver GD and the source driver SD on the basis of the signal S′ output from the signal converter 91. The gate driver GD is connected to the gate bus line of the liquid crystal panel of the scanning antenna 1000A, and supplies a scanning signal to the gate electrode of the TFT in accordance with the control signal received from the control circuit 92. In addition, the source driver SD is connected to the source bus line of the liquid crystal panel and supplies a data signal to the source electrode of the TFT in accordance with the control signal received from the control circuit 92. The timing controller 95 controls the control circuit 92 and the signal converter 91.

The signal converter 91 includes a look-up table (LUT) memory 96, an arithmetic circuit 97, and the VHR monitoring circuit MD. The VHR monitoring circuit MD includes the pulse voltage supply circuit 93 and the voltage monitoring circuit 94.

The pulse voltage supply circuit 93 is controlled by the timing controller 95. As described with reference to FIG. 26A, the pulse voltage supply circuit 93 outputs the pulse voltage to the first measurement electrode ME1 of the VHR monitoring capacitance C_(MV). Subsequently, the voltage monitoring circuit 94 monitors the change in the potential of the first measurement electrode ME1 at the voltage monitor 99. The voltage monitoring circuit 94 obtains the voltage holding ratio of the VHR monitoring capacitance C_(MV) on the basis of the output of the voltage monitor 99 and outputs the obtained voltage holding ratio to the arithmetic circuit 97.

The timing at which the pulse voltage supply circuit 93 outputs the pulse voltage can be freely set. For example, the pulse voltage may be output according to a predetermined operation by the user (for example, when the power is turned on). Alternatively, the pulse voltage may be output at regular intervals (for example, 30 seconds). Of course, these may be combined.

The arithmetic circuit 97 generates the signal S′ by referring to the input signal S, the output (for example, the voltage holding ratio of the VHR monitoring capacitance C_(MV)) from the voltage monitoring circuit 94, and the look-up table stored in the look-up table memory 96. The arithmetic circuit 97 may also be controlled by the timing controller 95. Note that the output from the voltage monitoring circuit 94 is not necessarily the voltage holding ratio of the VHR monitoring capacitance C_(MV), and may, for example, be the output voltage of the voltage monitor 99. In this case, in a case where the relationship between the output voltage of the voltage monitor 99 and the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit is obtained in advance, it is possible to determine the gray scale voltage to be supplied to each antenna unit according to the output voltage of the voltage monitor 99. In the following, a case in which the voltage holding ratio of the VHR monitoring capacitance C_(MV) is output from the voltage monitoring circuit 94 to the arithmetic circuit 97 will be described as an example.

At least one look-up table is stored in the look-up table memory 96. The look-up table stored in the look-up table memory 96 includes, for example, a two-dimensional matrix structure of 2 rows×4 columns as shown in Table 1. By referring to the look-up table in Table 1, one gray scale voltage is determined from the combination of the voltage holding ratio of the VHR monitoring capacitance CMV and the gray scale (from 0 gray scale level to 3 gray scale level) corresponding to the input signal. In Table 1, the voltage holding ratio of the VHR monitoring capacitance CMV is x %.

TABLE 1 Gray scale level Gray scale voltage (V) 0 1 2 3 VHR 30 ≤ x ≤ 100 0 1.8 3.0 15 [%] x < 30 0 2.3 3.9 15

The look-up table of Table 1 includes values of different gray scale voltages with respect to the gray scale corresponding to the input signal. The driving circuit 90 of the scanning antenna 1000A can generate different gray scale voltages with respect to a certain gray scale (for example, a certain intermediate gray scale) in the case that the voltage holding ratio (x %) of the VHR monitoring capacitance C_(MV) is greater than or equal to 30% and the case that it is less than 30%. Here, the intermediate gray scale does not include the highest gray scale or the lowest gray scale.

The scanning antenna 1000A can suppress the occurrence of the problem in that the voltage applied to the liquid crystal layer shifts from the target value due to the decrease in the voltage holding ratio of the liquid crystal capacitance, thus the phase difference provided to each microwave by each antenna unit shifts from the target value, and as a result, the gain decreases.

The look-up table stored in the look-up table memory 96 of the scanning antenna 1000A is not limited to that shown in Table 1. For example, it may have a two-dimensional matrix structure of 3 rows×4 columns as shown in the look-up table shown in Table 2. Also in Table 2, the voltage holding ratio of the VHR monitoring capacitance C_(MV) is x %.

TABLE 2 Gray scale level Gray scale voltage (V) 0 1 2 3 VHR 40 ≤ x ≤ 100 0 1.8 3.0 15 [%] 20 ≤ x < 40 0 2.0 3.4 15 x < 20 0 2.3 3.9 15

As shown in the look-up table shown in Table 3, for example, in the look-up table stored in the look-up table memory 96 of the scanning antenna 1000, one gray scale voltage may be determined from the combination of the ratio (x/x₀) of the voltage holding ratio (x %) of the VHR monitoring capacitance C_(MV) to the reference value (set as x₀%) of the voltage holding ratio and the gray scale (from 0 gray scale level to 3 gray scale level) corresponding to the input signal. The value of the reference value (x_(0%)) of the voltage holding ratio can be set to a freely-selected value depending on, for example, the environment in which the scanning antenna 1000A is used. The reference value x₀% of the voltage holding ratio is 30%, for example.

TABLE 3 Gray scale level Gray scale voltage (V) 0 1 2 3 VHR x/x₀ > 1.1 0 1.8 3.0 15 [%] 0.9 ≤ x/x₀ ≤ 1.1 0 2.0 3.4 15 x/x₀ < 0.9 0 2.3 3.9 15

The look-up table stored in the look-up table memory 96 may include values of different gray scale voltages with respect to the gray scale corresponding to the input signal, and is not limited to the look-up tables exemplified in Table 1 to Table 3. For example, the look-up table memory 96 may store a plurality of types of one-dimensional look-up tables corresponding to the value of the voltage holding ratio of the VHR monitoring capacitance C_(MV), and each one-dimensional look-up table may have a structure in which one gray scale voltage is listed with respect to the gray scale (from 0 gray scale level to 3 gray scale level) corresponding to the input signal S. That is, the look-up table memory 96 may store a plurality of types of look-up tables with gray scale voltages that differ from each other with respect to the gray scale corresponding to the input signal S. (For an example of a one-dimensional look-up table, see Table 4 below, for example) At this time, the signal converter 91 refers to a look-up table corresponding to the value of the voltage holding ratio of the VHR monitoring capacitance C_(MV) of the look-up tables stored in the look-up table memory 96.

The number of gray scales is not limited to the exemplified four gray scales, and can be modified as necessary. Any well-known driving method for the LCD panels can be applied as the driving method of the scanning antenna 1000A. In the LCD panels, a driving method of using a look-up table corresponding to 256 gray scales (from 0 gray scale to 255 gray scale) is well known. In addition, by using a look-up table having a two-dimensional matrix structure, for example, one gray scale voltage may be determined from a combination of a gray scale corresponding to the input signal S in the current vertical scanning period and a gray scale corresponding to the input signal S in the previous vertical scanning period. In this case, the signal converter 91 further includes a frame memory that retains an image corresponding to at least one vertical scanning period of the input signal S.

In the look-up table, combinations of all gray scales may not be listed, and only the combinations of certain gray scales may be listed. The arithmetic circuit 97 may generate the gray scale voltages corresponding to the combinations not listed in the look-up table by performing an interpolation operation on the basis of the listed combination. In this way, by limiting the combinations listed in the look-up table, the capacity required for the look-up table 96 can be reduced.

Instead of referring to the look-up table stored in the look-up table memory 96, the arithmetic circuit 97 may perform an arithmetic operation for determining the gray scale voltage from the input signal S. In this case, the relationship between the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gray scale voltage to be supplied for each antenna unit may be obtained in advance.

The driving circuit 90 may determine the gray scale voltage to be supplied to each antenna unit on the basis of not only the VHR monitoring capacitance C_(MV) but also the temperature of the liquid crystal panel. The driving method of the scanning antenna 1000A may further include a step of determining a gray scale voltage to be supplied to each antenna unit on the basis of the temperature of the liquid crystal panel. The scanning antenna 1000A may further include a temperature sensor 40.

For example, the look-up table memory 96 stores a plurality of look-up tables corresponding to the temperature of the liquid crystal panel. That is, the look-up table memory 96 includes different gray scale voltage values for the combinations of the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gray scale corresponding to the input signal. The look-up table 96 may include a plurality of types of look-up tables in which the values of the gray scale voltages differ from each other with respect to the combinations of the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gray scale corresponding to the input signal.

As illustrated in FIG. 27, the temperature of the liquid crystal panel is detected by the temperature sensor 40 and output to the arithmetic circuit 97. The arithmetic circuit 97 generates the signal S′ by referring to the input signal S, the output from the voltage monitoring circuit 94, the panel temperature detected by the temperature sensor 40, and the look-up table stored in the look-up table memory 96. The arithmetic circuit 97 generates the signal S′ with reference to the look-up table for the temperature closest to the panel temperature detected by the temperature sensor 40 from among the look-up tables stored in the look-up table memory 96, for example. The temperature sensor 40 is provided for example, in the transmission and/or reception region R1.

The driving method of the scanning antenna according to the embodiments of the disclosure may include a step in which a user determines a gray scale voltage to be supplied to each antenna unit according to the voltage holding ratio of the VHR monitoring capacitance C_(MV).

A scanning antenna 1000B of the embodiments of the disclosure differs from the scanning antenna 1000A in that a user determines the gray scale voltage to be supplied to each antenna unit according to the voltage holding ratio of the VHR monitoring capacitance C_(MV). The driving circuit 90 included in the scanning antenna 1000B and a driving method of the scanning antenna 1000B will be described with reference to FIG. 28. FIG. 28 is a block diagram schematically illustrating the driving circuit 90 included in the scanning antenna.

The driving circuit 90 of the scanning antenna 1000B differs from the driving circuit 90 of the scanning antenna 1000A in that the gray scale voltage supplied to each antenna unit is not determined on the basis of the voltage holding ratio of the VHR monitoring capacitance C_(MV). In the driving circuit 90 of the scanning antenna 1000B, after obtaining the voltage holding ratio of the VHR monitoring capacitance C_(MV) on the basis of the output of the voltage monitor 99, the voltage monitoring circuit 94 does not output the obtained voltage holding ratio to the arithmetic circuit 97, but outputs it such that a user can recognize it. Subsequently, the user determines the gray scale voltage to be supplied for each antenna unit according to the voltage holding ratio of the VHR monitoring capacitance C_(MV). The output from the voltage monitoring circuit 94 is not necessarily the voltage holding ratio of the VHR monitoring capacitance C_(MV), and may be the output voltage of the voltage monitor 99, for example. In this case, the relationship between the output voltage of the voltage monitor 99 and the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit may be obtained in advance.

The scanning antenna 1000B can also suppress the occurrence of the problem in that the voltage applied to the liquid crystal layer shifts from the target value due to the decrease in the voltage holding ratio of the liquid crystal capacitance, thus the phase difference provided to each microwave by each antenna unit shifts from the target value, and as a result, the gain decreases.

The look-up tables stored in the look-up table memory 96 of the scanning antenna 1000B include, for example, a one-dimensional matrix structure as shown in Table 4, and one gray scale voltage is stored with respect to the gray scales (from 0 gray scale level to 3 gray scale level) corresponding to the input signal S. The arithmetic circuit 97 generates the signal S′ by referring to the input signal S and the look-up table.

TABLE 4 Gray scale level 0 1 2 3 Gray scale voltage (V) 0 1.8 3.0 15

Manufacturing Method of Scanning Antenna 1000A

An example of a manufacturing method of the scanning antenna 1000A will be described.

First, the manufacturing method of the TFT substrate 100A will be described below. Note that the description of matters that are similar to those of the manufacturing method of the TFT substrate 101 described with reference to FIG. 5 may be omitted.

A gate conductive film is formed on the dielectric substrate 1 and the base insulating film 2, and a gate conductive film is patterned to form a gate metal layer. The gate metal layer includes the gate electrode 3 and the gate bus line GL in the transmission and/or reception region R1, and includes the first measurement electrode connection section 3 p 1 and the second measurement electrode connection section 3 p 2 in the non-transmission and/or reception region R2.

The gate insulating layer 4, the semiconductor layer 5, the source metal layer, and the first insulating layer 11 are formed in this order on the gate metal layer.

Subsequently, by collectively etching the gate insulating layer 4 and the first insulating layer 11 (that is, the insulating layer 13), the opening 13 a that reaches the first measurement electrode connection section 3 p 1 is formed in the gate insulating layer 4 and the first insulating layer 11. In this step, the opening 13 b that reaches the second measurement electrode connection section 3 p 2 may be further formed in the gate insulating layer 4 and the first insulating layer 11.

Next, a patch conductive film is formed on the first insulating layer 11, and in the opening 13 a and in the opening 13 b, and the patch conductive film is patterned to form a patch metal layer. The patch metal layer includes the patch metal layer 15 in the transmission and/or reception region R1 and includes the first measurement electrode ME1 in the VHR monitoring capacitance section MV of the non-transmission and/or reception region R2. The first measurement electrode ME1 is formed on the first insulating layer 11 and in the opening 13 a, and is in contact with the first measurement electrode connection section 3 p 1 within the opening 13 a. The patch metal layer may further include a seal region section 15 ps in the seal region Rs of the non-transmission and/or reception region R2. The seal region section 15 ps is formed on the first insulating layer 11 and in the opening 13 b, and is in contact with the second measurement electrode connection section 3 p 2 within the opening 13 b.

Next, the second insulating layer 17 is formed on the patch metal layer and the first insulating layer 11.

Subsequently, by collectively etching the second insulating layer 17, the first insulating layer 11, and the gate insulating layer 4 (that is, the second insulating layer 17 and the insulating layer 13), the contact hole CH7 that reaches the first measurement electrode connection section 3 p 1 and the contact hole CH8 that reaches the second measurement electrode connection section 3 p 2 are formed in the second insulating layer 17, the first insulating layer 11, and the gate insulating layer 4.

Subsequently, a transparent conductive film is formed on the second insulating layer 17, and the transparent conductive film is patterned. In this manner, the TFT substrate 100A is formed.

Subsequently, a manufacturing method of the slot substrate 200A will be described. Note that the description of the matters similar to those of the above-described manufacturing method of the slot substrate 201 may be omitted.

A metal film is formed on the dielectric substrate 51 and the third insulating layer 52, and this is patterned to form a layer including the slot electrode 55. The layer including the slot electrode 55 may be referred to as a “slot metal layer” in some cases. The slot metal layer includes the slot electrode 55, the extending section 55 e of the slot electrode, and the second measurement electrode ME2 in the VHR monitoring capacitance section MV of the non-transmission and/or reception region R2.

Next, the fourth insulating layer 58 is formed on the slot metal layer. Subsequently, in the seal region Rs of the non-transmission and/or reception region R2, the opening 58 a for exposing a part of the extending section ME2 e of the second measurement electrode ME2 is formed.

Thereafter, a transparent conductive film is formed on the fourth insulating layer 58, and the transparent conductive film is patterned. In this way, the slot substrate 200A is formed.

Resin Structure

The scanning antenna according to the embodiments of the disclosure may further include a resin structure between the first measurement electrode ME1 and second measurement electrode ME2, and the seal region Rs. FIG. 29A is a schematic plan view of the non-transmission and/or reception region R2 of a scanning antenna 1000A1 including a resin structure 75A, and FIG. 29B is a schematic plan view of the non-transmission and/or reception region R2 of a scanning antenna 1000A2 including a resin structure 75B. The scanning antennas 1000A1 and 1000A2 differ from the scanning antenna 1000A in that they include the resin structures 75A or 75B.

As illustrated in FIG. 29A, the scanning antenna 1000A1 further includes the resin structure 75A between the first measurement electrode ME1 and second measurement electrode ME2, and the seal region Rs.

When the resin structure 75A is provided between the first measurement electrode ME1 and second measurement electrode ME2, and the seal region Rs, it is possible to prevent the ionic impurities that elute (arising from uncured components, for example) from the seal resin 73 that forms the seal region Rs to the liquid crystal layer LC from reaching the liquid crystal layer LC of the VHR monitoring capacitance section MV. Accordingly, the liquid crystal layer LC of the VHR monitoring capacitance section MV is less likely to be affected by the seal resin 73 that forms the seal region Rs, and the voltage holding ratio of the VHR monitoring capacitance C_(MV) can be prevented from differing greatly from the voltage holding ratio of the liquid crystal capacitance Clc of the antenna unit region.

The influence of the ionic impurities that elute from the seal resin 73 to the liquid crystal layer LC will be described. It is conceivable to use an epoxy resin composition (for example, an amine-curable epoxy resin composition including an amine compound as a curing agent) including an epoxy resin or a curing agent as the seal resin 73. For example, the reaction between a liquid crystal material including an isothiocyanate group (—NCS) and an amine included in the curing agent is illustrated below.

Since the —NH—CS—NH— included in the product of the reaction formula of Formula 2 has a strong polarity, the deterioration of the liquid crystal material can be accelerated by such a reaction. Such a product may precipitate in the liquid crystal material. The case is not limited to that of using amines, and compounds having a strong polarity can be produced even when the seal resin 73 contains diazide or the like as a curing agent. In addition, the case is not limited to a liquid crystal material including an isothiocyanate group, and a compound having a strong polarity can also be produced by a liquid crystal material including a thiocyanate group (—SCN).

It is preferable that the resin structure 75 be formed from a material which does not react with the isothiocyanate groups or the thiocyanate groups of the liquid crystal material to produce a highly polarized compound. For example, an epoxy resin composition that includes no amine or diazide as a curing agent can be used. A resin material including an epoxy resin and inorganic particles may be used. The inorganic particles include, for example, Si, Mg, Ca, and any oxides thereof. The diameter of the inorganic particles is from 2 μm to 6 μm, for example. The diameter of the inorganic particles may be approximately the same as the thickness of the liquid crystal layer LC. The surface of the inorganic particles may be covered with an organic material. Polysiloxane (—(Si(X¹)(X²)—O)_(n)—) or R¹—Si(OR²)₃ can be used as the organic material (a polymeric material or a silane coupling agent, for example) that covers the surface of the inorganic particles, for example. Here, X¹ and X² are the same or different from each other, and each is a hydroxyl group, a methoxy group, an ethoxy group, or an alkoxy group having an alkyl chain of 1 to 24 carbon atoms. R¹ is a saturated alkyl group or an unsaturated alkyl group having from 1 to 18 carbon atoms, and R² is a hydrocarbon group, a methyl group, or an ethyl group.

The resin structure 75A may be formed on the TFT substrate 100A or the slot substrate 200A.

The height of the resin structure 75A is, for example, from 1 μm to 12 μm. The height of the resin structure 75A may be the same as the thickness of the liquid crystal layer LC, for example. That is, the height of the resin structure 75A may be the same as the height of the spacer that defines the thickness of the liquid crystal layer. Alternatively, the height of the resin structure 75A may be lower than the height of the spacer that defines the thickness of the liquid crystal layer LC.

As illustrated in FIG. 29A, the resin structure 75A has a shape in which a plurality of columnar structures, for example, are arranged when viewed from the normal direction of the TFT substrate 100A or the slot substrate 200A. The resin structure 75A may extend along a direction in which the seal region Rs extends, for example, when viewed from the normal direction of the TFT substrate 100A or the slot substrate 200A.

As illustrated in FIG. 29B, the shape of the resin structure 75B of the scanning antenna 1000A2 is different from that of the resin structure 75A. The resin structure 75B included in the scanning antenna 1000A2 has a wall shape, for example.

Columnar Metal

The scanning antenna according to the embodiments of the disclosure may include at least one columnar metal around the first measurement electrode ME1 and the second measurement electrode ME2. FIG. 30 is a schematic plan view of a scanning antenna 1000A3 including a columnar metal 77. The scanning antenna 1000A3 differs from the scanning antenna 1000A in that it includes a plurality of columnar metals 77.

As described above, a voltage is applied from the first measurement electrode ME1 and the second measurement electrode ME2 to the liquid crystal layer LC of the VHR monitoring capacitance section MV. At this time, there is a possibility that the effective voltage applied to the liquid crystal layer LC of the VHR monitoring capacitance section MV changes due to the influence of the electrical field in the antenna unit region U (in particular, the influence of the electrical field from the antenna unit region U that is close to the VHR monitoring capacitance section MV). The columnar metal 77 can suppress the influence of the electrical field from the antenna unit region U on the liquid crystal layer LC of the VHR monitoring capacitance section MV.

The columnar metal 77 may be formed on the TFT substrate 100A or on the slot substrate 200A. Preferably, the columnar metal 77 is formed on the slot substrate 200A, and is electrically connected to the slot electrode 55.

The diameter of the columnar metal 77 is from 2 μm to 6 μm, for example, and the height of the columnar metal 77 is from 2 μm to 6 μm, for example. The height of the columnar metal 77 may be the same as the thickness of the liquid crystal layer LC, for example. That is, the height of the columnar metal 77 may be the same as the height of the spacer that defines the thickness of the liquid crystal layer LC. Alternatively, the height of the columnar metal 77 may be lower than the height of the spacer that defines the thickness of the liquid crystal layer LC.

For example, the columnar metal 77 may be provided on an area closer to at least the transmission and/or reception region R1 among the periphery of the first and second measurement electrodes ME1 and ME2. The plurality of columnar metals 77 may be arranged, for example, at regular intervals.

Of course, the scanning antenna according to the embodiments of the disclosure may include both the resin structure 75A or 75B and the columnar metals 77, as illustrated in FIG. 31. FIG. 31 is a schematic plan view of a scanning antenna 1000A4 including the resin structure 75A and the columnar metal 77. The scanning antenna 1000A4 differs from the scanning antenna 1000A in that it includes a resin structure 75A and the plurality of columnar metals 77. The scanning antenna 1000A4 differs from the scanning antenna 1000A1 in that it includes a plurality of columnar metals 77.

EXPERIMENTAL EXAMPLES

The scanning antenna 1000A illustrated in FIG. 22 was manufactured as follows, and the scanning antenna of Example 1 was obtained.

The TFT substrate 100A and the slot substrate 200A were prepared. An alignment film was provided on the surfaces of the TFT substrate 100A and the slot substrate 200A disposed closer to the liquid crystal layer. After a rubbing treatment was performed on the alignment film, a sealing member was applied to one substrate so as to form a predetermined pattern. The TFT substrate 100A and the slot substrate 200A were bonded together, and a liquid crystal material having an isothiocyanate group was injected by a vacuum injection method. A 6254 type VHR measurement system available from TOYO Corporation was connected to the first measurement electrode ME1 and the second measurement electrode ME2 as a VHR monitoring circuit MD.

In this way, the scanning antenna of Example 1 was obtained. In the scanning antenna of Example 1, the first and second measurement electrodes ME1 and ME2 were disposed at positions separated by 10 mm or more from the seal region Rs.

In addition, the scanning antenna 1000A4 illustrated in FIG. 31 was manufactured as follows, and the scanning antenna of Example 2 was obtained. A manufacturing method of the scanning antenna of Example 2 differs from that of the scanning antenna of Example 1 in the following points. After preparing the TFT substrate 100A and the slot substrate 200A, the resin structure 75A (material: epoxy resin, height: 5 μm) and the columnar metals 77 (material: Al, diameter: 5 μm, height: 5 μm) were formed on one of the substrates (here, the slot substrate).

A scanning antenna including the driving circuit 90 illustrated in FIG. 28 was manufactured by the same method as that of the scanning antenna of Example 1, and the scanning antenna of Reference Example 1 was obtained. The driving circuit 90 of the scanning antenna of Reference Example 1 differs from the driving circuit 90 of the scanning antenna 1000 of Example 1 in that the gray scale voltage supplied to each antenna unit is not determined according to the voltage holding ratio of the VHR monitoring capacitance C_(MV). In addition, in the scanning antenna of Example 1, the look-up table memory 96 stores the look-up table shown in Table 1, whereas in the scanning antenna of Reference Example 1, the look-up table memory 96 stores the look-up table shown in Table 4.

As described below, the voltage holding ratio of the VHR monitoring capacitance C_(MV) in the scanning antennas of Example 1, Example 2, and Reference Example 1 were measured as Experimental Examples 1 to 5 and Comparative Example 1.

Experimental Example 1

The voltage holding ratio of the VHR monitoring capacitance C_(MV) was measured in the scanning antenna of Example 1. The measurement was carried out by leaving the scanning antenna statically in a thermostat at 70° C. The pulse voltage supplied to the first measurement electrode ME1 was a voltage having a pulse width of 60 μs, a pulse interval of 16.7 ms, an amplitude voltage of ±1 V. and a polarity that is inverted for each pulse. The potential of the second measurement electrode ME2 was 0 V.

Experimental Example 2 (High Temperature Storage Aging Test)

The scanning antenna of Example 1 was stored in a thermostatic chamber kept at 95° C. and a relative humidity of 10% for 240 hours, after which the voltage holding ratio of the VHR monitoring capacitance C_(MV) was measured. The measurement was carried out under the same conditions as those of Experimental Example 1.

Experimental Example 3 (High Temperature and High-Humidity Storage Aging Test)

The scanning antenna of Example 1 was stored in a thermostatic chamber kept at 60° C. and a relative humidity of 95% for 240 hours, after which the voltage holding ratio of the VHR monitoring capacitance C_(MV) was measured. The measurement was carried out under the same conditions as those of Experimental Example 1.

Experimental Example 4

In the scanning antenna of Example 2, the voltage holding ratio of the VHR monitoring capacitance C_(MV) was measured. The measurement was carried out under the same conditions as those of Experimental Example 1.

Experimental Example 5

The scanning antenna of Example 1 was placed statically in a room maintained at 25° C. and driven with a polarity inversion frequency (driving frequency) of 120 Hz while the data signal Vda supplied to the source bus line was set to ±15 V. Under this condition, the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gain of the scanning antenna were measured. With the exception that the voltage holding ratio was measured in a room maintained at 25° C., the voltage holding ratio was measured under the same conditions as those of Experimental Example 1. With regard to the gain of the scanning antenna, the maximum gain was measured in the range from 12.2 GHz to 12.6 GHz during reception.

Comparative Example 1

The scanning antenna of Reference Example 1 was placed statically in a room maintained at 25° C., and driven with a polarity inversion frequency (driving frequency) of 120 Hz while the data signal Vda supplied to the source bus line was set to ±15 V. Under this condition, the voltage holding ratio of the VHR monitoring capacitance C_(MV) and the gain of the scanning antenna were measured. Here, the user did not determine the gray scale voltage to be supplied to each antenna unit on the basis of the voltage holding ratio of the VHR monitoring capacitance C_(MV). The measurement was carried out under the same conditions as those of Experimental Example 5.

Experiment Results

The results of Experimental Examples 1 to 3 are shown in FIG. 32. FIG. 32 is a graph in which time (in seconds) is taken on the horizontal axis and the potential (in volts) of the first measurement electrode ME1 is taken on the vertical axis.

The measurement results of the voltage holding ratio in Experimental Examples 1 to 3 were 96%, 37%, and 54%, respectively. The measurement result of the voltage holding ratio in Experimental Example 4 was 97%, which was approximately 1% greater than that in Experimental Example 1. Note that the voltage holding ratio is the ratio (percentage) of the integral value of the voltage, from the start of pulse voltage application to 16.7 milliseconds after the application of the pulse voltage, with respect to the integral value in the case that the amplitude value (for example, 1 V in FIG. 32) of the pulse voltage is assumed to remain for 16.7 milliseconds.

The results of Experimental Example 5 and Comparative Example 1 are shown in Table 5.

TABLE 5 VHR 100% VHR 15% Experimental 32.1 dBi 31.8 dBi Example 5 Comparative 32.1 dBi 31.5 dBi Example 1

In Experimental Example 5 and Comparative Example 1, as the liquid crystal capacitance decreases, the gain of the antenna decreases. However, in Experimental Example 5, the decrease in the gain of the antenna when the voltage holding ratio was low was suppressed in comparison with Comparative Example 1. In the scanning antenna of Experimental Example 5, the gray scale voltage is supplied on the basis of the voltage holding ratio of the VHR monitoring capacitance C_(MV) using the look-up table of Table 1. It can be understood that such driving can prevent a problem from occurring, the problem that the voltage applied to the liquid crystal layer shifts from the target value due to the decrease in the voltage holding ratio of the liquid crystal capacitance, thus the phase difference provided to each microwave by each antenna unit shifts from the target value, and as a result, the gain decreases.

The scanning antenna according to the embodiments of the disclosure is housed in a plastic housing as necessary, for example. The housing is preferably formed of a material having a small dielectric constant ε_(M) that does not affect microwave transmission and/or reception. In addition, the housing may include a through-hole provided in a portion thereof corresponding to the transmission and/or reception region R1. Furthermore, the housing may include a light blocking structure such that the liquid crystal material is not exposed to light. The light blocking structure is, for example, provided so as to block the light incident on the liquid crystal layer by propagating through the dielectric substrate 1 and/or 51 from the side surface of the dielectric substrate 1 of the TFT substrate 101 and/or the side surface of the dielectric substrate 51 of the slot substrate 201. A liquid crystal material having a large dielectric anisotropy Δε_(M) may be prone to photodegradation, and as such it is preferable to shield not only ultraviolet rays but also short-wavelength blue light from among visible light. By using a light-blocking tape such as a black adhesive tape, for example, the light blocking structure can be easily formed in necessary locations.

INDUSTRIAL APPLICABILITY

Embodiments according to the disclosure are used in scanning antennas for satellite communication or satellite broadcasting that are mounted on mobile bodies (ships, aircraft, and automobiles, for example) or the driving methods thereof.

REFERENCE SIGNS LIST

-   1 Dielectric substrate -   2 Base insulating film -   3 Gate electrode -   4 Gate insulating layer -   5 Semiconductor layer -   6D Drain contact layer -   6S Source contact layer -   7D Drain electrode -   7S Source electrode -   7 p Source connection wiring line -   11 First insulating layer -   13 Insulating layer -   15 Patch electrode -   15 p Patch connection section -   17 Second insulating layer -   18 g, 18 s, 18 p Opening -   19 g Gate terminal upper connection section -   19 p Transfer terminal upper connection section -   19 s Source terminal upper connection section -   21 Alignment mark -   23 Protective conduction layer -   51 Dielectric substrate -   52 Third insulating layer -   54 Dielectric layer (air layer) -   55 Slot electrode -   55L Lower layer -   55M Main layer -   55U Upper layer -   55 c Contact surface -   57 Slot -   58 Fourth insulating layer -   60 Upper connection section -   65 Reflective conductive plate -   67 Adhesive layer -   68 Heater resistive film -   70 Power feed device -   71 Conductive beads -   72 Power feed pin -   73 Sealing portion -   90 Driving circuit -   91 Signal converter -   92 Control circuit -   93 Pulse voltage supply circuit -   94 Voltage monitoring circuit -   95 Timing controller -   96 Look-up table memory -   97 Arithmetic circuit -   98 i, 98 p Operational amplifier (amplifier) -   99 Voltage monitor -   101, 102, 103, 104 TFT substrate -   201, 203 Slot substrate -   1000 Scanning antenna -   CH1, CH2, CH3, CH4, CH5, CH6 Contact hole -   GD Gate driver -   GL Gate bus line -   GT Gate terminal section -   SD Source driver -   SL Source bus line -   ST Source terminal section -   PT Transfer terminal section -   IT Terminal section -   LC Liquid crystal layer -   MD VHR monitoring circuit -   ME1 First measurement electrode -   ME2 Second measurement electrode -   MV VHR monitoring capacitance section -   R1 Transmission and/or reception region -   R2 Non-transmission and/or reception region -   Rs Seal region -   U, U1, U2 Antenna unit, Antenna unit region 

The invention claimed is:
 1. A scanning antenna including a transmission and/or reception region including a plurality of antenna units and a non-transmission and/or reception region located in a region other than the transmission and/or reception region, the scanning antenna comprising: a TFT substrate including a first dielectric substrate, a plurality of TFTs supported by the first dielectric substrate, a plurality of gate bus lines, a plurality of source bus lines, and a plurality of patch electrodes; a slot substrate including a second dielectric substrate, and a slot electrode formed on a first main surface of the second dielectric substrate; a liquid crystal layer provided between the TFT substrate and the slot substrate; and a reflective conductive plate disposed opposing a second main surface of the second dielectric substrate opposite to the first main surface with a dielectric layer interposed between the reflective conductive plate and the second dielectric substrate, wherein the slot electrode includes a plurality of slots disposed corresponding to the plurality of patch electrodes, at least one monitoring capacitance section formed in the non-transmission and/or reception region and including the liquid crystal layer and a monitoring capacitance including a first measurement electrode and a second measurement electrode opposing each other with the liquid crystal layer interposed between the first measurement electrode and the second measurement electrode, and a voltage monitor connectable to the first measurement electrode of the monitoring capacitance.
 2. The scanning antenna according to claim 1, further comprising: a pulse voltage supply circuit including an amplifier electrically connectable to the first measurement electrode; and a feedback circuit configured to negatively feed back an output of the amplifier via the monitoring capacitance.
 3. The scanning antenna according to claim 1 further comprising: a monitoring auxiliary capacitance electrically connected to the monitoring capacitance.
 4. The scanning antenna according to claim 1, further comprising: a circuit configured to receive an output of the voltage monitor and obtain a voltage holding ratio of the monitoring capacitance; and a circuit configured to determine, based on the voltage holding ratio, a gray scale voltage to be supplied to each of the plurality of antenna units.
 5. The scanning antenna according to claim 1, wherein the first measurement electrode is formed from a conductive film identical to a conductive film of the plurality of patch electrodes, and the second measurement electrode is formed from a conductive film identical to a conductive film of the slot electrode.
 6. The scanning antenna according to claim 1 further comprising: a sealing portion formed in the non-transmission and/or reception region and surrounding the liquid crystal layer, wherein the first measurement electrode and the second measurement electrode do not overlap a region of less than 10 mm from the sealing portion when viewed from a normal direction of the first dielectric substrate.
 7. The scanning antenna according to claim 1 further comprising: a sealing portion formed in the non-transmission and/or reception region and surrounding the liquid crystal layer, wherein the TFT substrate or the slot substrate includes a resin structure between the first measurement electrode or the second measurement electrode and the sealing portion.
 8. The scanning antenna according to claim 1, wherein the TFT substrate or the slot substrate includes a plurality of columnar metals around the first measurement electrode or the second measurement electrode in the non-transmission and/or reception region, and the plurality of columnar metals include a columnar metal provided between the first measurement electrode or the second measurement electrode and the transmission and/or reception region.
 9. The scanning antenna according to claim 1 further comprising: a driving circuit configured to receive an input signal providing a gray scale to be exhibited by the plurality of antenna units, and supply a gray scale voltage to each of the plurality of antenna units, wherein the driving circuit can supply a gray scale voltage, based on an output of the voltage monitor.
 10. A method for driving the scanning antenna according to claim 1, the method comprising: obtaining, based on an output of the voltage monitor, a voltage holding ratio of the monitoring capacitance; and determining, based on the voltage holding ratio, a gray scale voltage to be supplied to each of the plurality of antenna units. 